The religious edifices were built between the decumanus and the imperial apartments. On one side was a mausoleum devoted to the emperor, while on the other were the temples of Venus and Cybele, now destroyed, and the temple of Jupiter, from whom Diocletian claimed to be descended. The sanctuary was transformed into a church devoted to St John the Baptist in the 6C, then used as the baptistery of the cathedral in the late 9C, hence its imposing baptismal fonts. The sphinx and bas-reliefs outside came from Egypt.