This terrace is to the west of horrea 28 and to the north of building 27. It faces the basin of Claudius. The western stretch is more than 200 metres long. The lower part is characterized by brick arches resting on travertine consoles. The back wall is made of opus reticulatum using basalt, to withstand the action of the waves. The actual terrace above is six metres deep. It had a white mosaic floor. Behind it is a porticus.
Below the terrace are two long corridors, 1.20 and 6 metres wide (opus latericium and mixtum). The first might be called a service corridor, the second a cryptoporticus. The latter was covered by cross-vaults. In the walls a horizontal drainage channel was embedded.
In late antiquity towers were set against the northern stretch, one of these on the corner between the two stretches. Lanciani mentions a total of fifteen towers set against both stretches. Apparently the terrace had now become part of the city wall.
The terrace on an old, undated photograph. Testaguzza 1970, p. 103.