is not contemporary with the castra, but earlier, dating to the time of Domitian. It was probably a nymphaeum of the Villa of Domitian. Later it was restored and incorporated into the Severan complex and used as a public baths or cult site. The first theory would explain the paviment of white and black mosaic tesserae with mythological figures, today located in the portico of the church. The second theory is supported by a peperino pagan altar and by some tombs found during archaeological excavations in 1935–38. After the Severan period, the structure was used as a granary or cult building, before conversion to a Christian building around the eighth century. The "thermae parvae" Some individual ruins in the ground near the piazza della Rotonda and Don Giovanni Minzoni Street have been called "thermae parvae" (Small Baths) in some reconstructions of the castra, to distinguish them from the "thermae magnae" (Large Baths), the Baths of Caracalla. These remains are under some houses on Don Giovanni Minzoni Street and are made up of two corridors, about a metre deep, one 2.70 metres long and the other 3.29 metres, with a series of niches along the walls. The construction was entirely carried out in opus reticulatum using peperino in the Severan period - it was the last building to use this technique in the Ager Romanus. These corridors are probably the cryptoportici of the bath, connected to other bathing rooms located in Piazza della Rotonda, near the modern Palazzo Vescovile. Soldiers' lodgings Not much remains of the buildings within the castra - some terraces, probably part of a barracks or soldiers' lodgings, have been found in the retentura (the part of the castra located between the praetorium and the porta decumana), inside the property of the episcopal seminary and the property of the Daughters of Immaculate Mary on San Fracesco d'Assisi Street. These ruins consist of five walls of the substructure arranged on different levels. On the second level, traces of a partition wall were found, which created rooms about 6 metres wide. During the archaeological excavations of 1915–1916, they found walls of 4.50 x 4.50 metre rooms in various constructive techniques on top of older walls dating back to the 1st century BC, all along San Francesco d'Assisi Street from the rectangular tower to the porta principalis sinistra. Further, indecipherable patterns of parallel walls were found in 1914 near the northwest