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Ricerche su Ostia e il suo territorio

 | 
Mireille Cébeillac-Gervasoni
, 
Nicolas Laubry
, 
Fausto Zevi

La necropoli di Porto all’Isola sacra : vecchie e nuove ricerche

Ostia beyond the Tiber : recent archaeological discoveries in the Isola Sacra

Paola Germoni, Simon Keay, Martin Millett and Kristian Strutt

Abstract

This article is a preliminary statement about the discoveries that have been made in the course of the geophysical survey of the Isola Sacra by the Portus Project in collaboration with the SS-Col since 2006. The work has made an important contribution to our understanding of the topography of the island with the discovery of many new sites, together with a major new canal which ran southwards from Portus towards the mouth of the Tiber. Of particular importance, however, was the discovery of a new northern sector of Ostia on the northern side of the Tiber. This area was composed of a suite of very large warehouses that were shut off from the rest of the Isola Sacra to the north by a defensive wall. This discovery transforms our understanding of the topography of Ostia, although there are still uncertainties about the chronology of both the warehouses and the defensive wall.

Full text

Introduction

  • 1 Keay et al. 2005, p. 277.

1The Isola Sacra is an artificial island, situated immediately north of the mouth of the Tiber (fig. 1). It is bounded to the south and east by the river, which turns to the south as it approaches the coast, flowing first southwards for c. 2 km, before turning again to the west to the sea. Until the river changed in course in 1557, there was a tight meander in the river at the point where it now turns towards the sea, so that it flowed around a narrow salient running to the east (fig. 2). This area was created as an island in the middle of the first century AD when, in preparation for the construction of a harbour at Portus, a pair of east-west canals was cut, connecting the Tiber directly with the coast. The more southerly of these which defines the northern limit of the Isola Sacra continued in use as the Fiumicino Canal, and is misleadingly still referred to in the archaeological literature as the Fossa Traiana even though there is very clear evidence that it was one of the canals referred to in the well-known inscription (CIL, XIV, 85) of AD 46 that records the construction of the canals in preparation for the building of Claudius’ harbour1. It is therefore clear that the Isola Sacra was created as an island as a by-product of the decision to build at Portus.

Fig. 1 – Location map of the Isola Sacra, showing Ostia Antica and Portus.

Fig. 1 – Location map of the Isola Sacra, showing Ostia Antica and Portus.

Fig. 2 – Map showing the Isola Sacra and the course of the Tiber, including topographic areas mentioned in the text, and the changing course of the ancient and modern Tiber caused by the 1557 inundation.

Fig. 2 – Map showing the Isola Sacra and the course of the Tiber, including topographic areas mentioned in the text, and the changing course of the ancient and modern Tiber caused by the 1557 inundation.

2The Isola Sacra thus extends for c. 2.6 km from north to south. The western limit of the island, formed by the Tyrrhenian coast, has been enlarged by the progradation of the Tiber delta since the Roman period, with the island now extending for c. 4.6 km from east to west. The Isola Sacra of the Roman period, however, measured only c. 1.6 km from east to west, creating a land area of c. 330 ha.

  • 2 Keay et al. 2005, p. 62–65. Two short seasons of geophysical survey were also conducted in the are (...)

3Although the land forming the island is very low lying and prone to flooding, it was clearly of immense significance after the establishment of the imperial harbour at Portus in the middle of the first century AD. It provided the terrestrial link between the harbour complex at Portus and the well-established urban community at Ostia, as represented by the road, the Via Flavia, which joins the two and probably dates to the Flavian period. Furthermore, as it represented a key area of land in the delta of the Tiber, an understanding of its use provides potential insights into the social and economic dynamics of Portus and Ostia as a connected working community. It was with this in mind that work in 2007–2012 by the Portus Project used techniques of geophysical and topographic survey as previously deployed at Portus to provide a new understanding of the whole of the Isola Sacra2.

Geological background

  • 3 Arnoldus-Huyzendveld et al. 2005.
  • 4 Bellotti et al. 1995, p. 618.
  • 5 Arnoldus-Huyzendveld et al. 2005.
  • 6 Salomon et al. 2016.
  • 7 Belluomini et al. 1986 ; Lambeck et al. 2004.

4The deposits of the present coastal plain at the mouth of the Tiber date to the Holocene transgression phase that occurred between 17,000 and 5,000 BP3. The river delta is subdivided into two parts (fig. 3) ; the inner delta comprises alluvial and marshy deposits while the outer delta consists of dune and beach ridges4. The area to the north of the river Tiber, known as the Agro Portuense, consists of marine, dune, lagoonal and alluvial deposits dating to the Holocene period, with the southern part of the delta, the Agro Ostiense, forming an area of lagoon deposits formed from the Stagno Ostiense5. The zone of the Isola Sacra is located in the central part of the delta, between the modern course of the river Tiber, and the so-called Fossa Traiana. It forms a strand plain and, as the delta has prograded since c. 6500BP, the Isola has extended westwards by about 1 m per year. Evidence for this is represented in the chronology of archaeological material across the modern Isola Sacra and in the presence of dipolar anomalies in the magnetometer survey results that mark strandlines in the formation of the delta6. Data for the Tiber delta based on borehole samples relied upon the dating of peat, marsh and wood fragments7. The tectonic action in the area has been interpreted as showing signs of a slow rate of uplift (0.15 ± 0.05 mm yr⁻¹) in the Late Holocene.

Fig. 3 – Map showing the principal geology and geomorphology for the area of the middle and lower Tiber and the Tiber Delta (derived from Borzi et al. 1998).

Fig. 3 – Map showing the principal geology and geomorphology for the area of the middle and lower Tiber and the Tiber Delta (derived from Borzi et al. 1998).
  • 8 Bellotti 1998.
  • 9 Arnoldus-Huyzendveld – Paroli 1995 ; Arnoldus-Huyzendveld et al. 1997.
  • 10 Arnoldus-Huyzendveld et al. 2005, p. 19.
  • 11 Bravard et al. 2017 in press

5The most prominent change to the form of the Isola Sacra and the course of the lower Tiber in the medieval and post-medieval period occurred at Ostia in 15578, when the river flooded and breached a bend in the river, changing its course9. During excavation at this point on the line of the Tiber, three phases of lateral meander displacement were noted ; one of Roman date, ascribable to the 1st century AD, and two dating to 1530 and 155710. The latter displacement truncated the south-east isthmus within the ancient bend in the Tiber, cutting off the area from the Isola Sacra and forming the Fiume Morto oxbow to the north-east of Ostia Antica11. It is difficult to imagine the topography of the ancient Tiber and the south-east part of the Isola Sacra, due to the modern constraints on the terrain formed by the river. However, an understanding of this is crucial to evaluating the results of the recent magnetometer surveys on the Isola Sacra, and the relationship between both banks of the Tiber in the formation and layout of Ostia.

The administrative context

  • 12 Soprintendenza Speciale per il Colosseo, Museo Nazionale Romano e Area Archeologica di Roma, previ (...)
  • 13 Germoni et al. 2011, p. 239-255.
  • 14 In the person of Dott.ssa Paola Germoni

6Our survey work on the Isola Sacra needs to be understood against the background of the long history of archaeological work that has focused on the island. The Isola Sacra exemplifies the history of protection of the archaeological heritage in Italy, and the fundamental role played by current regulatory requirements (dispositivi normativi vigenti). These permit research that is intended to promote the understanding and conservation of cultural heritage that is in the public interest, including that undertaken on private property. The SS-Col12 have played a key role in implementing this in recent years, coordinating and undertaking development-led excavations and watching briefs on a range of sites. The area coloured in red on fig. 4 has been declared of archaeological interest under D.Lgs 42/04, with similar concentrations of significant Roman settlement closer to Ostia and Portus standing in contrast to the less intensively settled areas in the centre of the Isola Sacra. This archaeological context was used in the creation of the Piano Regolatore Generale, the foremost urban planning document used in modern urban contexts (fig. 5). In the Piano Regolatore Generale, the territory of the Isola Sacra is sub-divided into Type 1 Archaeological Areas and Type 2 Areas of Archaeological Interest, with different technical norms for each type, making preventative archaeology possible within and outside of the context of large public works. The results are summarised in the accompanying archaeological map that includes discoveries up until 2012 (fig. 6). This was previously published as part of a study of past work on the Isola Sacra, and includes a full gazetteer, much of which remains otherwise largely unpublished13. One of the objectives of our survey, which was undertaken in close collaboration with the SSCol14, was to use new information from systematic survey to enhance existing efforts at protecting the archaeological heritage by providing information about hitherto undiscovered sites.

Fig. 4 – Map showing the areas declared Beni di Interesse Culturale in the sense of the articles 10, 13, 15 and 45 of the D.Lds. 42/04 and similar.

Fig. 4 – Map showing the areas declared Beni di Interesse Culturale in the sense of the articles 10, 13, 15 and 45 of the D.Lds. 42/04 and similar.

Fig. 5 – Piano Regolatore Generale of the Comune di Fiumicino, approved by the Regione Lazio on the 31-03-2006 with DGR – 162/2006, allegato A.

Fig. 5 – Piano Regolatore Generale of the Comune di Fiumicino, approved by the Regione Lazio on the 31-03-2006 with DGR – 162/2006, allegato A.

Fig. 6 – Fiumicino – Isola Sacra. Archaeological map updated to 2012. The red square indicates the location of the Roman ships.

Fig. 6 – Fiumicino – Isola Sacra. Archaeological map updated to 2012. The red square indicates the location of the Roman ships.

Previous archaeological discoveries in the Isola Sacra

  • 15 Germoni et al. 2011 : sites 36, 37 and 38.
  • 16 Germoni et al. 2011 : site 3.

7Roads were a defining characteristic of the Isola Sacra. The Via Flavia was the most important of these, and acted as the main axis of communication between Portus and Ostia from at least the later 1st century AD onwards. Stretches of the road discovered to date indicate that it had a width of up c. 10 m and that while some sections had a surface of basalt blocks akin to consular roads leading out of Rome, others were composed of rammed gravel between stone retaining margins (fig. 6 : sites 36, 37 and 38)15. Another key stretch of road, with basalt paving, ran along the south side of the Fossa Traiana (fig. 6 : site 3)16.

  • 17 With reference made to the site numbers used in the gazetteer published in Germoni et al. 2011.
  • 18 Cf. Veloccia Rinaldi – Testini 1975, p. 43-151.

8A glance at the gazetteer for the Isola Sacra as a whole in fig. 6 highlights a series of key features relating to the topography of the island that may be summarized briefly17. Three broad zones of activity have been revealed, comprising the southern edge of the Fossa Traiana in the north, areas beside the Via Flavia to the west, and the stretch along the northern side of the Tiber to the south, the latter being the least extensively explored. The northern area includes evidence for the statio marmorum (fig. 6 ; site 28a) that lay close to the junction of the canal with the river at the north-east corner of the island, Capo Due Rami. Further west along the canal there is evidence for a series of quays and associated structures (fig. 6 : sites 1, 3, 4, 5, 12). Set back behind these there were buildings belonging to a settlement centred on the point where the Via Flavia crossed the canal via a bridge. Exploration in this area in the 1970s uncovered structures relating to the port quarter in the vicinity of the later basilica dedicated to Saint Hippolytus, including a bath house (fig. 6 : sites 12, 13, 14)18 and further towards the coast a complex identified as an Isaeum (fig. 6 : site 7). In the area to the south of this settlement there were extensive burials, including some substantial mausolea (fig. 6 : sites 11, 16, 18-24, 27, 30).

  • 19 Cf. Calza 1940.

9In the western part of the Isola, activity is focused on the line of the Via Flavia which runs north-south just inland from the Roman coast and separated from it by a band of sand dunes, the inland movement of which later covered and preserved the Roman landscape. The known remains from this area are dominated by the well-known Necropoli di Porto (fig. 7) excavated in the 1930s (fig. 6 : site 35)19, but further burials have also been explored, linking this cemetery with those noted above (fig. 6 : sites 32, 34-5).

Fig. 7 – Aerial view of the Necropoli di Porto along the Via Flavia, located to the south of the Terme di Matidia and Sant’Ippolito (S. Keay).

Fig. 7 – Aerial view of the Necropoli di Porto along the Via Flavia, located to the south of the Terme di Matidia and Sant’Ippolito (S. Keay).
  • 20 Boetto et al. 2012 ; Boetto – Germoni – Ghelli 2014 ; Boetto – Ghelli – Germoni in press ; Fiore e (...)
  • 21 Zevi 1972, p. 406-407.

10Recent discoveries are starting to suggest that the southern part of the Isola Sacra was far more significant than has been previously thought to have been the case. Small funerary sites and occasional single burials have been identified in the vicinity of the Via Flavia (fig. 6 : sites 39 and 40) some distance to the south of the Necropoli di Porto. Still further to the south, rescue excavations in advance of preparatory work for a new bridge over the Tiber on the eastern margin of the Via della Scafa revealed the remains of two ships of 2nd century AD date (fig. 6 : Red Square)20. These perhaps need to be understood in relation to a Roman bridge over the Tiber between the Isola Sacra and Ostia, and known from unpublished archival evidence (fig. 6 : site 50). To the east of this, structures identified in the late 1960s suggest the northwards expansion of Ostia from the first century AD to the late antique period. Small-scale excavations revealed evidence of warehouses (fig. 6 : sites 41-46)21.

The context of the current survey work

  • 22 Otherwise known as the Necropoli dell’Isola Sacra : Calza 1940 ; Baldassarre 1978.
  • 23 Germoni et al. 2011 : site 14.
  • 24 Germoni et al. 2011 : site 7.
  • 25 Germoni et al. 2011 : site 12.
  • 26 Keay et al. 2005.

11The discoveries discussed in this paper have to be understood, first of all, in the context of the long-standing programme of overseeing the protection of the archaeological heritage in the Isola Sacra by the SS-Col. Some of the sites discussed in section 4 were first discovered in the early 20th century, while others have been the subject of major campaigns of excavation, most notably the Necropoli di Porto22, but also the church of Sant’ Ippolito (fig. 6 : site 14)23, the Isaeum (fig. 6 : site 7)24 and the Terme di Matidia (fig. 6 : site 1225) immediately to the south of the Fossa Traiana. Knowledge of the existence of many others, however, has been the work of the Ostia office of the SS-Col, which has recorded sites that have been revealed by building works and clandestine activities. While this approach was clearly successful in recording sites accidentally revealed by intrusive activities, it could only ever be a response to circumstance. The SS-Col was quick to recognize the success of the geophysical survey at Portus26 in locating hitherto unknown sites in areas between the hexagonal basin and the Tiber, and to calculate that the adoption of similar blanket coverage of the Isola Sacra would greatly support their efforts in protecting its buried heritage. This interest coincided with the research strategy of the Portus Project that was keen to use geophysical survey to learn more about the topography of the Roman Isola Sacra and, thus, the relationship of Portus to Ostia. The discoveries discussed here, therefore, are the result of a joint programme of heritage management and research.

Brief description of the main discoveries between the Fossa Traiana and the Tiber

12Results of the geophysical surveys from 2007 to 2012 identified a large number of different monuments, sites and features across the Isola Sacra, that are best discussed in order. A series of linear and rectilinear anomalies were found along the Tiber (fig. 8), marking the presence of tombs and mausoleum enclosures fronting onto the river. The western extents of these features were generally identified with their eastern facades extending under the modern flood defences along the Tiber bank.

Fig. 8 – Greyscale image of the magnetometer survey results from along the Tiber, showing possible tombs and enclosures in the fields adjacent to the river, and under the dike situated alongside the river.

Fig. 8 – Greyscale image of the magnetometer survey results from along the Tiber, showing possible tombs and enclosures in the fields adjacent to the river, and under the dike situated alongside the river.
  • 27 Germoni et al. forthcoming.

13One important observation about the magnetometry results is that road alignments lack definition, and in some stretches even appear to be absent. The results of the magnetometry survey and recent excavations suggest that one of the reasons for this is because some of the roads were constructed from gravel and beaten earth27, meaning that it is difficult for the magnetometer to detect them. At some points along the line of the Via Flavia, the road surface is rendered invisible by a covering layer of dune deposits. Clearly these features would respond more positively to a more integrated approach, utilising air photographic evidence together with GPR and resistivity survey. Together, these should better detect the characteristic variations in moisture content and interfaces between materials of different density caused by the surface of the roads.

14A system of regularly-spaced parallel alignments and negative linear features (fig. 9) may form part of an orthogonal network of drainage ditches or channels that ran from east to west across the Isola Sacra. It is interesting to note that these features run from the back of the Necropoli di Porto, but at a slight tangent to the alignment of the tombs located within the excavated area and the line of the Via Flavia. Their alignment also runs at an angle of 25º to the line of the 19th and 20th century Bonifica drainage ditches, suggesting that they relate at least in part to an ancient field system or artificial drainage system.

Fig. 9 – Greyscale image of the magnetometer survey results, showing ditch features traversing the Isola Sacra.

Fig. 9 – Greyscale image of the magnetometer survey results, showing ditch features traversing the Isola Sacra.
  • 28 Germoni et al. 2011 ; Salomon et al. 2016.
  • 29 Keay et al. 2005, p. 126.
  • 30 Keay et al. 2005.

15In addition to this field system, the dominant feature located in the 2009 survey results is a massive canal running from north to south across the survey area, from the Fossa Traiana in the north towards the mouth of the Tiber to the south (fig. 10)28. The western edge of this feature is only poorly defined, predominantly where it cuts through dipolar deposits. The eastern edge is better defined and this may suggest some form of revetment similar to other canal features elsewhere at Portus29. The canal that these features define measures some 90m across close to the line of the Fossa Traiana in the north, although it narrows quite significantly as it heads southwards towards the mouth of the Tiber. It is feasible that this feature is a continuation of the Canale Romano to the north of the Fossa Traiana located to the south of the hexagonal basin at Portus30. The line of the canal is traversed by a series of positive features, one of which is still visible as the opus caementicium pier belonging to a bridge that would have crossed the line of the canal. From this point southwards the canal widens to 90 m, and the pattern of sediment showing in the feature suggests that the central portion of the canal silted up, possibly forming a small island. The later narrower bands of sediment are visible to either side of this feature.

Fig. 10 – Greyscale image of the magnetometer survey results showing the northern portion of the newly found canal (right hand side of image) running from north to south across the Isola Sacra.

Fig. 10 – Greyscale image of the magnetometer survey results showing the northern portion of the newly found canal (right hand side of image) running from north to south across the Isola Sacra.

16The southernmost part of the Isola Sacra provided the most exciting results in the survey (fig. 11). A substantial area of settlement measuring at least 600 m by 200 m was located in the results of the magnetometry. A series of structures are visible in the results, many suggesting a form reminiscent of excavated warehouses in Ostia to the south of the river Tiber. These are discussed in more detail below.

Fig. 11 – Greyscale image of the magnetometer survey results from the south of the Isola Sacra, indicating the warehouses and defensive wall circuit.

Fig. 11 – Greyscale image of the magnetometer survey results from the south of the Isola Sacra, indicating the warehouses and defensive wall circuit.

17Several substantial archaeological features were also recorded close to the line of the modern Via Redipuglia (fig. 12) in the north of the Isola Sacra. In particular a large structure was found to have been cut by the line of the modern road. This may form part of a complex of buildings and related deposits located along and to the north of the road around the church of Sant’ Ippolito. The evidence from the geophysical survey, together with the Isola Sacra site gazetteer, suggests that there was a concentration of structural remains in this zone of the Isola, potentially associated with the Fossa Traiana and the Statio Marmorum.

Fig. 12 – Interpretative image of the magnetometry from the area of the Via Redipuglia.

Fig. 12 – Interpretative image of the magnetometry from the area of the Via Redipuglia.

A preliminary description of the warehouses and the northern wall circuit

  • 31 Germoni et al. 2011 : sites 41-46 ; Zevi 1972, p. 406-407.

18The principal features identified in the survey in the southern part of the Isola Sacra relate to a previously unknown defensive wall and a series of warehouses and other large buildings that line the bank of the Tiber. Elements of these latter structures had been discovered in the 1960s, but the circumstances of that work meant that they could not be explored on a very large scale31.

19The defensive wall can be traced clearly from the present bank of the Tiber in the east, running in a line for c. 345 m to the west south-west (fig. 13). This orientation is shared both by a pair of boundaries to the south, and by the general alignment of the Roman field systems revealed by our survey further to the north of the Isola Sacra. Along this stretch, the wall is about 3-5 m thick, and has three rectangular external towers (6 m x 8 m) placed about 80 m apart. A probable fourth tower lies partly beneath the trackway a further 74 m to the west. To the east, the wall has clearly been cut by the river when it changed course in the 16th century, but we may note that its projected line would have run close to the northern edge of the projected continuation of the island before the river moved.

Fig. 13 – Interpretation image of the survey results from the southern part of the Isola Sacra.

Fig. 13 – Interpretation image of the survey results from the southern part of the Isola Sacra.

20To the west, the wall changed course, turning to run north-south, but this corner was in an area unavailable for survey. A 75 m stretch of the north-south course is visible in the survey, ending about 20 m short of one of the warehouses. Here, restrictions on the area available for survey mean that its course could not be mapped. One possibility is that it turned again to the west, to run along parallel with the river, while another is that followed the western side of the warehouse.

21Given the character of this wall and especially the provision of external towers, there can be no doubt that this is a town wall delimiting the settlement on this side of the Tiber. Its layout and relationship to other boundaries found in the survey suggests that it was laid-out as part of a broader planned landscape. Its dating is discussed further below.

22In the area enclosed between the wall and the present course of the Tiber, the survey has produced evidence for a series of major buildings, all aligned broadly with the river. The evidence is somewhat fragmented because it was not possible to survey the whole area, but there is sufficient evidence to understand the basic layout, although the all-important relationship between the buildings and the river remains obscure.

  • 32 Rickman 1971, p. 24-30.
  • 33 Germoni et al. 2011, site 42 ; Zevi 1972, buca 2.

23There is evidence for five principal buildings, some only fragmentary. From the west, the first and most completely understood building is a courtyard warehouse c. 175 m wide and more than 175 m long (Building 1). It appears to comprise a range of store rooms facing onto a portico that surrounded a courtyard ; the plan of its southern part is uncertain, but there is possibly a second courtyard towards the river frontage. The form of this building bears similarities to the layout of the Grandi Horrea and the Piccolo Mercato at Ostia, supporting its identification as an horreum, although the latter is smaller in size32. Adjoining this building to the east, and sharing a common boundary, is a further courtyard building, with storerooms similarly opening onto a portico (Building 2). The western range extends for at least 75 m, whilst the northern that lies at an obtuse angle can be traced for about 25 m. This is almost certainly a further rectangular horreum. There is a gap in our survey data to the east of this building, with enough space to contain a further horreum of similar size. The next building to the east (Building 3) is represented by a building section of similar form, with a north-south range of store rooms facing a portico to the west, which can be reasonably interpreted as the eastern range of this. The row of storerooms excavated in the 1960s33 that lie to the south of almost certainly formed part of the same building.

24The north-east corner of another courtyard building has been located further to the north-east, but this is set back considerably further from the river. It is also slightly different in plan, with rooms only visible in its eastern range, and these are of different proportions and flanked by a corridor on both sides (Building 4). This arguably suggests a different function, with no clear parallels amongst the structures excavated at Ostia. Finally, closest to the Tiber at the eastern edge of the Isola there is a further large building on the same alignment and again set back from the river to the south, although very different in form (Building 5). It is about 50 m wide and at least 50 m deep, divided into two by a north-south wall. The space to the west contains three or perhaps four rows of regularly spaced columns c. 8 m apart. The function of the building is uncertain, although the differences between its layout and those of the other buildings to the west would argue seem to against it being a warehouse. The character of the rooms to the east is less clear.

Initial interpretation of the discoveries

25A key characteristic of the geophysical results in the area around Buildings 1 to 5 is the relatively « quiet » background, with very little evidence for any other structures. This would suggest that the warehouses were not preceded by earlier structures, a hypothesis that is supported by the fact that none of the excavated sondages in this area revealed any residual Republican pottery, although admittedly the sample of published material is very limited.

26In terms of the buildings themselves, it is important to recognize that none of them are per se dateable. The nature of the magnetometry evidence is such that the chronology of detected structures can only be roughly gauged, either in terms of clearly differing structural alignments, or through their similarity to other published structures of known date. Nevertheless, there is enough circumstantial evidence to provide us with a rough indication.

  • 34 Coarelli 1994, p. 39.

27The orientation of the buildings respects the roughly east-west orientation of the field divisions that were detected across the rest of the Isola Sacra by the geophysical survey, suggesting that the two were broadly contemporary. This alignment is also shared by the Via degli Aurighi and Via della Foce and associated buildings at the western end of Ostia ; it differs, however, from the orientation of the street grid centred upon the Castrum and the Decumanus Maximus to the east. What this signifies is unclear. F. Coarelli argues that the area between the Via del Foce and the Tiber was related to the early port, which lies further to the west, even though the chronology of some of the standing buildings would appear to date to the 2nd century AD34.

  • 35 However. F. Coarelli (1994, p. 39) argues that the area between the Via della Foce and the Tiber m (...)
  • 36 Zevi 1972, p. 407.
  • 37 Zevi 1972, p. 407.
  • 38 Coarelli 1994, p. 40-42.
  • 39 Calza 1921.

28Overall, therefore, the evidence we have points to a date rather later than the initial development of Ostia between the late 4th century and 1st century BC35. This is supported to some degree by the chronology of the structures excavated in the late 1960s. A date of the 1st century AD was assigned to structures in buca 1 that probably belonged to the southern side of Building 136. Furthermore, the construction technique of the walls found in buca 2, found to the south of Building 3, was dated to the 2nd centurt AD37. The similarity of the plan of Building 1 to the Grandi Horrea at Ostia, dateable to some time between c. 100 BC38 and the reign of Claudius39, would tend to support this hypothesis. It is also similar to the layout of the Piccolo Mercato dated to between AD 119-120. Taken together, this evidence would suggest that the buildings probably dated to some time during the 1st or earlier 2nd centuries AD.

29There is little doubt that the stretch of the defensive walls running from east to west across the survey area is the most unexpected result of the survey, with profound implications for our understanding of the topography of Ostia as a whole. Our principal challenge at the moment, however, is to date the period of their construction. Some indication can be gained by looking at their structural relationship to the warehouses. At the western end of their course, the walls turn sharply southwards in the direction of the northern wall of Building 1 : the results are not sufficiently clear to be sure that the walls directly abutted it. This would suggest one of two possibilities. Either they preceded the construction of Building 1 and were cut by the northern wall of the warehouse when it was constructed in the 1st or 2nd century AD. Alternatively, they could have been built at some date after the construction of Building 1 in an attempt to incorporate the standing walls of the structure into the defensive circuit. Since the geophysical readings close to the point of junction are not entirely clear, this relationship is an issue that can only be resolved by excavation. The existence of a very strong magnetic anomaly running down the western side of Building 1, however, might be an argument in support of the latter possibility.

  • 40 Zevi 1996-1997.
  • 41 Coarelli 1994, p. 39-42 ; Zevi 2002, p. 54-57.
  • 42 Calza et al. 1953, p. 79-88.
  • 43 We would like to thank Dr. Carlo Rosa for this information.

30The most obvious question is to ask whether the walls represent a northward continuation of the 63-58 BC wall circuit known from east and southern sides of Ostia40. It has been argued for the area south of the Tiber between the Castrum and the Porta Romana being an area for the unloading and transhipment of grain and other goods from the 2nd century BC prior to storage in warehouses running along the south side of the Decumanus Maximus41, and it would be tempting to see the warehouses on the north side of the Tiber playing a complementary role. However, the characteristics of the walls would seem to argue against this. They are c. 3-5 m wide, square towers (6 m x 8 m) that were located on straight stretches of wall and faced out northwards. This stands in contrast to the walls on the eastern and southern sides of Ostia, even though published evidence is admittedly slim. These had a thickness of 2.5 m, while the towers were circular, much less frequent than on the Isola Sacra wall, and were situated at internal angles rather than on straight stretches42. However, one recent aerial photograph has revealed parch marks that show evidence for a single external square tower, although it is unclear whether or not this was a later addition to the original scheme43.

  • 44 Keay et al. 2005, p. 106-112, 284-285 and 291-293. Although this stretch of wall has not been date (...)
  • 45 Procop., Goth., 5, 26, 9.

31There are thus significant differences between the Isola Sacra wall and the rest of the Ostia wall circuit. This, together with the likely early Imperial date of the warehouses, would argue in favour of a date for the walls at some time after the 1st to 2nd century AD. How much later than this is hard to establish, although there would not seem to be any prima facie administrative context for the construction of the northern circuit in the course of the early Imperial period. This would leave the late antique period as the most likely horizon for their creation, even though there is no firm evidence to assign them a late antique date. One argument in favour of this would be the similarity of the arrangement of the internal stretch of late antique wall at Portus known as the Contramura Interna and which included the Arco di Santa Maria. This is comprised of exterior facing square towers c. 7 m x 8 m and is dated to c. AD 48044. It should be noted, however, that Procopius, writing about events ninety years later in c. AD 570, notes that Ostia was « without walls »45.

Implications of the discoveries for our understanding of Ostia (fig. 14)

Fig. 14 – Map of the southern sector of Isola Sacra in relation to the ancient and modern courses of the Tiber and Ostia. In particular, it shows the position of the newly discovered warehouses in relation to the Portus to Ostia canal, the Via Flavia, the harbour basin of Ostia and the mouth of the Tiber (F. Salomon).

Fig. 14 – Map of the southern sector of Isola Sacra in relation to the ancient and modern courses of the Tiber and Ostia. In particular, it shows the position of the newly discovered warehouses in relation to the Portus to Ostia canal, the Via Flavia, the harbour basin of Ostia and the mouth of the Tiber (F. Salomon).
  • 46 Heinzelmann 2002, Abb. 1.

32It is now clear that in general topographic terms, Ostia encompassed a much larger ground area than had previously been thought. The geophysical survey undertaken by M. Heinzelmann in the 1990s revealed that during the Imperial period, the southern sector of the port extended for up to c. 300 m beyond the line of the 1st century BC wall46. Our work has shown that it also extended northwards beyond the line of the Tiber for a similar distance. Although our survey only covered the area between the Ponte della Scafa and the modern bend of the river, there is every reason to expect a similar spread of buildings between the latter and the ancient river meander at the Fiume Morto, an area in which structures have indeed been reported. In this new topographic reality, we have to re-think the general layout of the port as being bisected by the Tiber, rather than delimited by it.

  • 47 Keay et al. 2005, p. 301-302, table 9.1.
  • 48 Working on the assumption that Building 1 covered very roughly 8667 m2 and that the other two ware (...)
  • 49 Heinzelmann 2002, taf. IV.2.

33Unlike the area lying to the south of the Decumanus Maximus and beyond, our quarter of Ostia « beyond the river » appears to have been largely given over to warehouses with no apparent residential occupation. The increase in storage capacity that this represents is very significant. Published evidence for total warehouse space at Ostia in the 2nd century AD was c. 31,882 m247. If we add to this a very crude estimate of the ground area of the three possible warehouses in the southern Isola Sacra, arguably in the order of magnitude of 26000m248, then the total storage space at Ostia rises to c. 57,882 m2. To this should probably be added the area lying between the modern bend in the Tiber and the Fiume Morto, as well as the yet unquantified and unpublished evidence for additional warehouses that has been revealed by geophysical survey within the southern half of the walled area of Ostia49.

34This very substantial increase in storage space raises important issues about the role of the river port as an entrepôt in the early Imperial period. It seems likely that much of what was stored here would have been destined for Rome, with some also retained for local consumption and presumably some also for re-distribution. Whatever views one takes on this issue, however, it is clear that it needs to take into account other aspects of port infrastructure in the Isola Sacra and Ostia, and the relationship between Ostia and Portus.

Towards a new perspective on the relationships between Ostia and Portus

35There is as yet very little evidence for any occupation of the southern side of the Isola Sacra prior to the early Imperial period. Following the creation of Portus in the mid 1st century AD, there was clearly a need to establish infrastructure that would enable it to function in conjunction with Ostia as a major transhipment and storage depot for imported foodstuffs and other supplies. The Via Flavia was the main element of this, running from the Fossa Traiana at Portus at a point close to the mouth of the Canale Trasverso, southwards to the Tiber at a point close to the modern Ponte della Scafa, opposite the small harbour basin at Ostia (fig. 14). The development of the warehouses in the southern sector of the Isola Sacra would seem to make most sense following the creation of the road, enabling goods bound for export and consumption to be moved more easily between Ostia and Portus.

  • 50 Keay 2012.

36The second element was the Portus to Ostia canal, which measured c. 90 m wide in the north to c. 25 m further south, and which was discussed above. It ran from a point on the Fossa Traiana roughly opposite the mouth of the Canale Romano southwards towards Ostia. While it seems to initially head for the Ostia harbour basin, it appears to veer gently south-westwards before reaching it and flowed into the Tiber close to its mouth. The two boats discovered near the Via della Scafa were found in a silty context that is probably to be identified with deposits relating to the canal. The date for the construction of the canal is uncertain, but would seem to make most sense in the context of the Trajanic replanning of Portus50.

  • 51 See for example Delaine 2002 ; Mar 2002, p. 144-153.
  • 52 Keay 2012.

37This new waterway would have complemented the Via Flavia and greatly facilitated the flow of traffic between Portus and Ostia. Indeed the possibility that Building 3 may have dated to the 2nd century AD is further evidence to the support arguments that the Trajanic enlargement of Portus and its associated infrastructure may have provided a significant stimulus to the construction of new warehouses and other buildings noted at Ostia in the course of the Trajanic and Hadrianic period51, particularly in the area between the Via degli Aurighi and the Tiber. All of this is further evidence for the idea that for the early and middle Imperial period at least both Ostia and Portus played complementary roles in what has been termed the port system of Imperial Rome52.

38The northern circuit is also a very significant discovery that would seem on balance to be best understood in the context of the late antique city rather than that of the late Republic or early Empire. If the late 5th century AD does prove to be the likely horizon for its construction, it suggests that it may have been constructed by the same authority that was responsible for building the walled circuit that enclosed much of the central area of Portus. While the identity or the motive for this remains unclear, it would probably make most sense in the early years of the Ostrogothic Kingdom of Theoderic.

  • 53 Pavolini 2016.

39The implications of this for Ostia are profound. While it has been argued that the port underwent some kind of economic reversal in the course of the 3rd century AD53, there is good evidence that it continued to act as some kind of administrative and ecclesiastical centre well into the 4th century AD if not later. If this wall circuit was constructed in the late 5th century AD, it would argue that the port had continued to play a role of some kind in supplying the City alongside Portus up until that date, or that it was part of an attempt to fortify the mouth of the Tiber.

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Salomon et al. 2016 = F. Salomon, S. Keay, J. P. Goiran, K. Strutt, M. Millett, P. Germoni, Connecting Portus with Ostia : Preliminary Results of a Geoarchaeological Study of the Navigable Canal on the Isola Sacra, in C. Sanchez, M. P. Jézégou (ed.), Les ports dans l’espace méditerranéen antique. Narbonne et les systèmes portuaires fluvio-lagunaires. Actes du colloque international tenu à Montpellier, 22-24 mai 2014, Montpellier-Lattes, 2016 (Supplément à la Revue archéologique de Narbonnaise, 44), p. 293-305

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Notes

1 Keay et al. 2005, p. 277.

2 Keay et al. 2005, p. 62–65. Two short seasons of geophysical survey were also conducted in the area surrounding the Terme di Matidia at the northern end of the Isola Sacra, in part as a training survey for students from the universities of Southampton and Cambridge, but also as a trial investigation of the zone prior to the Portus Project surveys from 2007-2012 (Strutt 2005). This work was funded by the Arts and Humanities Research Council, and supported by the University of Southampton, the British School at Rome and the University of Cambridge, in collaboration with the Soprintendenza Speciale per i Beni Archeologici di Roma.

3 Arnoldus-Huyzendveld et al. 2005.

4 Bellotti et al. 1995, p. 618.

5 Arnoldus-Huyzendveld et al. 2005.

6 Salomon et al. 2016.

7 Belluomini et al. 1986 ; Lambeck et al. 2004.

8 Bellotti 1998.

9 Arnoldus-Huyzendveld – Paroli 1995 ; Arnoldus-Huyzendveld et al. 1997.

10 Arnoldus-Huyzendveld et al. 2005, p. 19.

11 Bravard et al. 2017 in press

12 Soprintendenza Speciale per il Colosseo, Museo Nazionale Romano e Area Archeologica di Roma, previously the Soprintendenza Speciale per i Beni Archeologici di Roma (Sede di Ostia), and the Soprintendenza per i Beni Archeologici di Ostia.

13 Germoni et al. 2011, p. 239-255.

14 In the person of Dott.ssa Paola Germoni

15 Germoni et al. 2011 : sites 36, 37 and 38.

16 Germoni et al. 2011 : site 3.

17 With reference made to the site numbers used in the gazetteer published in Germoni et al. 2011.

18 Cf. Veloccia Rinaldi – Testini 1975, p. 43-151.

19 Cf. Calza 1940.

20 Boetto et al. 2012 ; Boetto – Germoni – Ghelli 2014 ; Boetto – Ghelli – Germoni in press ; Fiore et al. 2015.

21 Zevi 1972, p. 406-407.

22 Otherwise known as the Necropoli dell’Isola Sacra : Calza 1940 ; Baldassarre 1978.

23 Germoni et al. 2011 : site 14.

24 Germoni et al. 2011 : site 7.

25 Germoni et al. 2011 : site 12.

26 Keay et al. 2005.

27 Germoni et al. forthcoming.

28 Germoni et al. 2011 ; Salomon et al. 2016.

29 Keay et al. 2005, p. 126.

30 Keay et al. 2005.

31 Germoni et al. 2011 : sites 41-46 ; Zevi 1972, p. 406-407.

32 Rickman 1971, p. 24-30.

33 Germoni et al. 2011, site 42 ; Zevi 1972, buca 2.

34 Coarelli 1994, p. 39.

35 However. F. Coarelli (1994, p. 39) argues that the area between the Via della Foce and the Tiber may have been the site of the early port of Ostia.

36 Zevi 1972, p. 407.

37 Zevi 1972, p. 407.

38 Coarelli 1994, p. 40-42.

39 Calza 1921.

40 Zevi 1996-1997.

41 Coarelli 1994, p. 39-42 ; Zevi 2002, p. 54-57.

42 Calza et al. 1953, p. 79-88.

43 We would like to thank Dr. Carlo Rosa for this information.

44 Keay et al. 2005, p. 106-112, 284-285 and 291-293. Although this stretch of wall has not been dated per se, it forms part of the late antique circuit. This has been dated to c. AD 480 by excavations at the Antemurale (Paroli – Ricci 2011, p. 140), and by Portus Project excavations in the vicinity of the Palazzo Imperiale.

45 Procop., Goth., 5, 26, 9.

46 Heinzelmann 2002, Abb. 1.

47 Keay et al. 2005, p. 301-302, table 9.1.

48 Working on the assumption that Building 1 covered very roughly 8667 m2 and that the other two warehouses were of similar size. This would exclude the large building closest to the modern course of the Tiber.

49 Heinzelmann 2002, taf. IV.2.

50 Keay 2012.

51 See for example Delaine 2002 ; Mar 2002, p. 144-153.

52 Keay 2012.

53 Pavolini 2016.

List of illustrations

Title Fig. 1 – Location map of the Isola Sacra, showing Ostia Antica and Portus.
URL http://books.openedition.org/efr/docannexe/image/3734/img-1.jpg
File image/jpeg, 1018k
Title Fig. 2 – Map showing the Isola Sacra and the course of the Tiber, including topographic areas mentioned in the text, and the changing course of the ancient and modern Tiber caused by the 1557 inundation.
URL http://books.openedition.org/efr/docannexe/image/3734/img-2.jpg
File image/jpeg, 380k
Title Fig. 3 – Map showing the principal geology and geomorphology for the area of the middle and lower Tiber and the Tiber Delta (derived from Borzi et al. 1998).
URL http://books.openedition.org/efr/docannexe/image/3734/img-3.jpg
File image/jpeg, 1,5M
Title Fig. 4 – Map showing the areas declared Beni di Interesse Culturale in the sense of the articles 10, 13, 15 and 45 of the D.Lds. 42/04 and similar.
URL http://books.openedition.org/efr/docannexe/image/3734/img-4.jpg
File image/jpeg, 858k
Title Fig. 5 – Piano Regolatore Generale of the Comune di Fiumicino, approved by the Regione Lazio on the 31-03-2006 with DGR – 162/2006, allegato A.
URL http://books.openedition.org/efr/docannexe/image/3734/img-5.jpg
File image/jpeg, 913k
Title Fig. 6 – Fiumicino – Isola Sacra. Archaeological map updated to 2012. The red square indicates the location of the Roman ships.
URL http://books.openedition.org/efr/docannexe/image/3734/img-6.jpg
File image/jpeg, 268k
Title Fig. 7 – Aerial view of the Necropoli di Porto along the Via Flavia, located to the south of the Terme di Matidia and Sant’Ippolito (S. Keay).
URL http://books.openedition.org/efr/docannexe/image/3734/img-7.jpg
File image/jpeg, 3,9M
Title Fig. 8 – Greyscale image of the magnetometer survey results from along the Tiber, showing possible tombs and enclosures in the fields adjacent to the river, and under the dike situated alongside the river.
URL http://books.openedition.org/efr/docannexe/image/3734/img-8.jpg
File image/jpeg, 2,6M
Title Fig. 9 – Greyscale image of the magnetometer survey results, showing ditch features traversing the Isola Sacra.
URL http://books.openedition.org/efr/docannexe/image/3734/img-9.jpg
File image/jpeg, 2,7M
Title Fig. 10 – Greyscale image of the magnetometer survey results showing the northern portion of the newly found canal (right hand side of image) running from north to south across the Isola Sacra.
URL http://books.openedition.org/efr/docannexe/image/3734/img-10.jpg
File image/jpeg, 2,6M
Title Fig. 11 – Greyscale image of the magnetometer survey results from the south of the Isola Sacra, indicating the warehouses and defensive wall circuit.
URL http://books.openedition.org/efr/docannexe/image/3734/img-11.jpg
File image/jpeg, 2,3M
Title Fig. 12 – Interpretative image of the magnetometry from the area of the Via Redipuglia.
URL http://books.openedition.org/efr/docannexe/image/3734/img-12.jpg
File image/jpeg, 2,5M
Title Fig. 13 – Interpretation image of the survey results from the southern part of the Isola Sacra.
URL http://books.openedition.org/efr/docannexe/image/3734/img-13.png
File image/png, 3,5M
Title Fig. 14 – Map of the southern sector of Isola Sacra in relation to the ancient and modern courses of the Tiber and Ostia. In particular, it shows the position of the newly discovered warehouses in relation to the Portus to Ostia canal, the Via Flavia, the harbour basin of Ostia and the mouth of the Tiber (F. Salomon).
URL http://books.openedition.org/efr/docannexe/image/3734/img-14.jpg
File image/jpeg, 1,2M

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