The Palazzo Imperiale
Fieldwork in spring and summer 2014 saw a continuation of the work on the Palazzo Imperiale. This is a c. 2 ha structure that is located upon an isthmus at the centre of the port, affording its occupants very clear views over the Trajanic and Claudian basins. It was established under the Emperor Trajan and was abandoned some time during the Byzantine period. This season was focused upon the range of rooms along the northern side of the complex, from the Castellum Aquae in the east (Building 1), westwards. Our fieldwork, part of a joint strategy of excavation and restoration, the latter being coordinated by the SS-Col, is investigating a zone (Area K) that lies on the western side of the early twentieth-century path that bisects the complex from north to south. This is a challenging part of the site, since it involves excavation of a partially standing structure, with archaeological remains on two storeys.
This rectangular opus testaceum room, initially uncovered in 2009 (Area D), was situated on both sides of the twentieth-century path that bisects the complex. The 2012 and 2013 excavations (Area K) revealed the full eastward extent of its walls, its internal layout around a central peristyle and opus spicatum flooring, and also paid particular attention to the southeastern sector of the room, revealing the stumps of the square pilasters that carried the vaults of the first-floor room above and confirming its rectangular peristyle-like structure. The 2014 work focused upon resolving the latest phases of activity in the western part of Building 3, in an area on the northern side of the piers that defined the northern side of the peristyle and the doorway that provided access into the western corridor of Building 8. Removal of overlying rubble facilitated access to levels relating to the latest activity (Period 6A) prior to the demolition of the Palazzo Imperiale in the mid-sixth century AD (Period 6C), most notably the robbing of lead piping.
This was a complex range of rooms on three storeys that continued the northern sector of the Palazzo Imperiale westwards. The first-floor rooms were arranged around a central peristyle (Room 8.9) that looked out northwards over the Claudian basin. Its central pool incorporated a combined light-well at first-floor level and rectangular cistern at ground-floor level. This scheme enabled a series of vaulted rooms opening off the cistern at ground-floor level to be illuminated by natural light. Today, only the ground and parts of the first floor survive. It is noticeable, however, that while the southern side of this range of rooms continued in a straight line westwards, the outer face of the northern range of rooms overlooking the Claudian basin ran at a northwesterly angle. Excavation in 2014 continued on the southern stretch of the ground floor of the north– south corridor (which had a sloping concrete floor) (Room 8.3), which separated the rooms of Building 8 from Building 3 to the east. It clarified our understanding of the stratigraphic sequence that was first uncovered in 2013, and fully revealed the plan of a square structure of third-century AD date (Period 4) that was built directly onto the surface of the corridor and abutted the east wall of Building 3. Since there was no evidence for any added flooring, wall lining or an entrance, its function remains unknown. Cleaning of the eastern wall surface of Room 8.14 on the opposite side of the corridor (Room 8.3), by contrast, revealed the window that would have enabled light from the corridor to illuminate the ground-floor room below 8.13. This confirms the idea developed in previous years that all of the ground-floor rooms were illuminated by windows on the eastern and western sides in the context of an ingenious architectural scheme for this part of the Palazzo Imperiale to maximize the percolation of daylight at ground- and first-floor levels. Excavation continued in the first-floor rooms. Rubble deriving from second-floor rooms was removed from Room 8.11 to reveal opus sectile imprints of Period 5 (fourth and early fifth centuries AD) and, in Room 8.9, just inside the door between 8.11 and 8.9 in the northern sector of the peristyle, the edges of a high-quality polychrome mosaic of possibly Trajanic date (Period 2); the latter undoubtedly formed part of the same floor as that uncovered further south in 2013. The large Room 8.15, which lies immediately to the west of Room 8.12 and on the northern side of the pool at the centre of the peristyle, was cleared of loose surface debris on its eastern side. This revealed the imprints of the opus sectile decoration, akin to that in Rooms 8.12 and 8.11, and also would have dated to between the fourth and early fifth centuries AD (Period 5). The similarity of this decoration to that of 8.12, which was excavated in 2013, provides further evidence for a wholesale redecoration of this residential part of the Palazzo Imperiale between the fourth and fifth centuries AD.
The south side of the Palazzo Imperiale
In order to ensure that our excavations encompassed the full breadth of this part of the northern range of the Palazzo Imperiale, a sondage was opened on the south side of Room 8.13 (Area E). Its precise position was chosen on the basis of the results of the 1998–2004 geophysical survey and the 2009 excavations. Both of them indicated that a corridor c. 5 m wide ran from east to west along the south side of Buildings 3 and 8, defining the southern edge of the Palazzo Imperiale and the open area between this and Building 5. The 2014 excavation confirmed this interpretation and also uncovered part of a Period 5 white mosaic floor with black border. Excavation on the south side of the corridor wall revealed a concrete podium and an adjacent concrete foundation projecting into the open area; the function of both of these remains unknown.
In order to understand better the character of the northern façade and quay of the Palazzo Imperiale, and their relationship to the Claudian basin, a small sondage was opened on the north side of Building 3 (Area K). It revealed the stepped character of the lower brick courses of the late antique (Period 6A) fortification that incorporated the Palazzo Imperiale and the opus caementicium mass of the quay below. As in the excavation of the corresponding stretch of quay to the east (Area B) in 2009, rich organic deposits from the silted up Claudian basin directly abutted the quay, on top of which there was a concrete platform belonging to a structure of some kind that continued northwards under the baulk of the excavation.
Building 5 (Navalia)
Building 5 lies immediately to the south of the excavated part of the Palazzo Imperiale, and formed part of the same original architectural concept. Fieldwork undertaken in 2011 and 2012 (Keay et al., 2012) revealed that it was a vast, single building measuring 240 Å~58 m that was organized into a series of regularly-spaced units oriented from north to south. Each of these was in turn subdivided in a consistent sequence: a passage 4 m wide, three narrow bays each c. 11 m wide, a passage 4 m wide, and a wide bay c. 19 m wide. All of these building sections opened on to a quayside bordering the Claudian basin to the north and on to a quayside bordering the Trajanic hexagonal basin to the south. Previous fieldwork revealed that the building was established under Trajan, when it seems to have had some kind of ship repair or construction function, and that in the later second century AD it was converted into a battery of warehouses that continued in use until at least the later fifth century AD. The 2014 excavations enlarged the Sondage 2 undertaken in 2013 by extending it eastwards across the full width of one of the narrow bays (B5.2/NB4). The aim was to cut through the late second/early third-century AD (Period 4) floor in order to reveal the character of the original Trajanic flooring, and thereby better understand the function of the bay. The excavations revealed a rammed cocciopesto surface of a later second century AD (Period 3) surface underlain by a complex series of overlapping discontinuous work surfaces that immediately post-dated the Trajanic (Period 2) floor. These appeared to slope gently eastwards and westwards from a central north– south rise. They were perforated on the eastern side by a series of stake-holes of different sizes, while the position of other posts was marked by the juxtaposition of tile supports; these results need to be understood in the context of the line of stake-holes found at the extreme western side of Sondage 2 in 2012. Clearly these were used to sustain a large structure of some kind. That this might be identified as a ship or boat is suggested by the discovery of numerous bronze and iron nails, as in 2012, but also various pieces of ironwork, and a small depression that may have been filled with pitch.