Built outside the Roman city walls, near the amphitheater from which it has taken most of its salvage materials, this extremely old religious building is of great importance not only for art history but also for all sacred Western Christian architecture. It can be compared to San Vitale of Ravenna and the Aquisgrana cathedral. It went through numerous renovations through the end of the 4th Century and the beginning of the 5th Century. There is a legend that the chapel was built by Galla Placidia, and it is thought that she is buried in the tomb on the right of the entrance. Outside there is a statue which is a copy of the statue of Constantine, who was made Emperor in 313, and gave freedom to the cult of Christianity. Also to be noted is the umbrella-shaped dome and fragments of early Christian mosaics.