The mosaic on the first arch facing the nave were originally made at the suggestion and expense of the empress Galla Placidia under Pope Leo the Great (440-461). Restorations in the ninth, twelfth, fourteenth, eighteenth, and nineteenth centuries have so changed the work that in all probability only the design remains of the original. The figures in the upper ⅔ are on a gold background. The Head of Christ is in the center, with his hand raised in blessing in the Byzantine manner, and to the sides are symbols of the Evangelists, the 24 Ancients of the Apocalypse and angels.