Attention was focused upon the Palazzo Imperiale, a major and highly luxurious administrative complex on the key promontory that separates the Claudian from the Trajanic basins. Geophysical and building surveys, and environmental coring were undertaken across the area, as well as a major programme of excavation. The work was directed by Simon Keay (University of Southampton/British School at Rome), with Graeme Earl (University of Southampton) and Fabrizio Felici (Parsifal Cooperativa, Rome), and with the very full support and collaboration of Lidia Paroli (Soprintendenza di Beni Archeologici di Ostia). The work was funded by the AHRC and the Soprintendenza di Beni Archeologici di Ostia e Porto, and involved participants from the Universities of Southampton, Cambridge, Rome (La Sapienza), Aix- en-Provence (Centre Camille Jullian), Tarragona (Institut Català d’Arqueologia Clàssica) and Seville. This work was central to the British School at Rome’s Roman Ports initiative.
The Pre-Trajanic Palazzo Imperiale
The discovery of the pre-Trajanic mole at the northern edge of the excavation is of major importance. It makes clear that the original line of the Claudian basin in this part of Portus did not project north-westwards as it did with the completed Palazzo Imperiale from the Trajanic period onwards. It appears instead that it extended in an arc south-westwards that coincides with the alignment of the westernmost side of the Trajanic hexagonal basin. This suggests that Trajan’s architects may have chosen the alignment of the Claudian basin in this part of the harbour as the reference point for the laying out of the hexagonal basin. A core drilled through the Trajanic mole (2007) revealed the existence of marine deposits beneath it suggesting that the area south of the pre-Trajanic mole may have been open water, and provides a hint that the pre-Trajanic harbour in this part of the port may have been lagoonal in nature.
The Palazzo Imperiale during the Second Century AD
This evidence from these excavations suggests gross modo that the Palazzo Imperiale was a construction de novo of late Trajanic date. As yet there are few good ceramic deposits to give us a clear date. However, the epigraphic fragments reported by Lanciani as having been found at the site indicate that an important stage in its construction had been reached by AD 112/117 even though their precise point of discovery within the complex remains unknown. Furthermore brick- stamps from both these excavations and those discussed by Bloch imply that construction continued until at least AD 115/116, with subsequent work continuing under Hadrian and the Antonines. This date would seem to be borne out in general terms by the opus reticulatum technique used in the brick-faced construction, while the Terrazza di Traiano has also been traditionally dated to the reign even though are no obvious dated stylistic parallels for it. The relationship of the Trajanic Palazzo Imperiale to the south- westerly alignment of the pre-Trajanic mole makes it clear that the former was built upon land re-claimed from the south-eastern corner of the Claudian basin, presumably up-cast displaced during the excavation of the hexagonal basin itself. The layout of the completed 3 Ha complex was distinctive. It was trapezoidal in shape, overlooked both the Claudian and Trajanic basins and was served by the large Open Area discovered during these excavations to the east. In order to better understand the significance of these developments within the context of the Palazzo Imperiale as a whole, the first results of the topographical and geophysical surveys of the remainder of the complex have been used to produce a summary plan of the whole of the first floor. This allowed broad functional areas to be identified on the basis of known standing structures and geophysical anomalies. The complex offered onumental facades to the west and south, but also had a more “functional” area to the east that was integral to Building 5. Fresh water consumption played an important role in its functions.
Subsequent Development of the Palazzo Imperiale
During the early third century AD, access to, and unloading within, Palazzo Imperiale by means of the Open Area was suppressed with the construction of the amphitheatre- shaped building and its associated courtyard and garden. Overall this suggests that the eastern side of the complex may have acquired a more residential or decorous function than hitherto, although it should be remembered that since this new building was effectively enclosed in the space between the Cistern Block and Building 5, it would only have been visible from that part of the Open Area lying to the east.
Late Antique Palazzo Imperiale
The principal topographic change during the late antique period saw the incorporation of the Palazzo Imperiale and Building 5 within the walled circuit that enclosed the whole port. In the case of the former, they adapted to the pre-existing topography and ran along the frontage of the building, while the corridors down to the Trajanic hexagon were systematically demolished to create a steep bank that sloped downwards from north to south. With the Palazzo Imperiale, however, the defences needed to run northwards and keep the Cistern Block within the walled area.
Consequently, the amphitheatre-shaped building and luxurious rooms lying to the west had to be demolished, thereby creating a flat open area behind the walls. It also defined an open area that lay between these stretches of wall, the Cistern Block (Buildings 1 and 2) to the north and Periods 1 and 2 moles. At one level the inclusion of both buildings within the walled circuit is testimony to their continued importance during the later fifth and sixth centuries, which is hardly surprising in itself. However, while corroborative data is needed from other parts of both complexes, this evidence does suggest that the construction of the late antique fortifications in the late 5th century AD represented a major change in the character and uses of both buildings. In the first instance it seems that the water within the Claudian basin had contracted quite significantly to the point where the old Period I mole was no longer at the water’s edge, and what had been a dock between the Period I and Period 2 moles had degenerated into a zone of passage frequented by people using the gateway in the fortifications.
In short, the Palazzo Imperiale had become landlocked, a development which may go some way to helping us understand the need for substantial fortifications in this part of the port, which may have been erected in response to both land and sea-based threats. Furthermore, the blocking of the gate in the sixth century is paralleled by a similar development at the Antemurale, raising the question as to whether gate- blocking was a coordinated response to external threat, possibly related to the Gothic wars. Secondly, Building 5 clearly cannot have continued to function as before since much of its northern part had been demolished, while the Palazzo Imperiale had lost a major monumental focus. The final and most significant development was the increasingly widespread excavation of burials within Palazzo Imperiale, Building 5 and in the open area to the north of the latter. This is testament to a use of space that was very different o that which had prevailed earlier.