This vast multi-purpose complex stands in the north-western sector of the city, not far from the Tiber.

The building that can be seen today dates to the period of the Antonine and Severan emperors (with its main phases dating to AD 145-150 and 190-200), but it was constructed over pre-existing structures.

General view of the complex during excavation
(P. Cacchiatelli, G. Cleter)

It served a variety of purposes, as we can deduce from the simultaneous presence of a building with a porticoed courtyard (A) with an adjoining mithraeum (B), a bath complex (C) and a row of shops facing the Tiber (D).

Floor mosaic from the calidarium of the baths
(P. Izzi)

Though we can now rule out its interpretation as the Ostian residence of the emperors, the discovery of a lead pipe (fistula) bearing the name of Matidia, Trajan’s niece, and the luxurious nature of the decorative programme suggest a direct connection to the Imperial family.

View of the mithraeum in the Palazzo Imperiale (B) (print of 1860)

Bases and statues of Cautes and Cautopates found in the mithraeum of the Palazzo Imperiale (B)