This building, partially excavated at the end of the 19th century, is directly to the east of the Grandi Horrea (II,IX,7), across the road. The walls are of Hadrianic opus mixtum. In the centre of the building is a large round structure. The scanty remains consist of a tufa circle, without podium. It has been suggested that it was a basin, and that the building was a fulling mill.

The round structure may also have been an oven. On an old plan a basin, a floor of basalt blocks and a round object (a millstone or kneading-machine?) seem to be indicated, two rooms to the north. Therefore the building may also have been a bakery. Excavation of the north part of the building will be helpful.

A number of rooms across the street (part of a row of rooms along the east side of the Grandi Horrea) also had floors of basalt blocks.