The Castellum Aquae
The so-called Castellum Aquae, is actually a three storey cistern block (Building 1) that also formed the eastern end of the northern range of the Palazzo Imperiale.
It was built in the Trajanic period. Its north side rested on the pre-Trajanic quay that defined the south side of the Claudian basin and on a Trajanic quay to the south. The cisterns themselves were situated on the first and second floor, with the ground floor acting as a service area: another, smaller two storey cistern (Building 2) was added to the east of this in the Hadrianic period.
Immediately to the west of the Castellum Aquae was another part of the Palazzo Imperiale, a very long room (Building 3) that in turn abutted a major complex of rooms focused upon a cistern/peristyle (Building 8). In the centre of the former was an open area around which ran a vaulted portico on three stories; the bases of the piers that supported the vaults can still be clearly seen.
This room was provided with an opus spicatum (brick herringbone) floor, typical of working or service areas in major buildings such as this. In the early third century, a small glass producing furnace was installed. To the south of Buildings 1 and 3 there was an open area that provided access to the eastern facade of the Palazzo Imperiale from the quayside to the east.
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