Built between 425 and 430, the Galla Placidia Mausoleum contains classic Roman-Hellenistic mosaics. These intact 5th century examples are the oldest and most complete mosaics found in Ravenna today.

The X-P symbol is chi-rho, the first two letters for Christ in Greek. The Greek letter alpha (A, the first letter of the Greek alphabet) on one side of the chi-rho and a Greek letter omega (looks like a W, the last letter of the Greek alphabet) on the other side signify the beginning and end. This symbology is derived from Jesus Biblical quote, "I am the alpha and the omega, the beginning and the end."