The seat of the bishop has a late-antique tower (opus vittatum) in the south-east corner. It was fortified in the Middle Ages, probably in relation to the invasions of the ninth century. There are several indications that the south part of Portus, to the west of the "internal wall", was the last line of defence.
An outer wall of the Episcopium. Photograph: Jan Theo Bakker.
A gate of the Episcopium. Photograph: Jan Theo Bakker.
The Episcopium on an old, undated photograph.
In the foreground is the Fossa Traiana. Testaguzza 1970, p. 216.