This large rotunda monument was built in 306 CE by the Emperor Galerius, possibly as his mausoleum. Unfinished, Constantine consecrated it as a Christian Church shortly thereafter. Extensive mosaics of precious materials and very high quality covered the interior. Today some of that original beauty remains in the dome area, as restoration proceeds. The photograph that is displayed to the left shows the frescoes that were added in the 9th century.

This church's early history is indicative of the upheaval in the development of Christianity in the 4th century. Galerius, a tetrarch of the Roman Empire who ruled an area which included Greece, persecuted the Christians, issuing an edict that was in place from 303-311, when he retracted it on his deathbed. How ironic that, within a few decades, the rotunda would become a magnificent Christian church. This may be the earliest Christian church building still in existence. [Janina K. Darling, Architecture of GreeceGreenwood, 2004, p. 84-86.]