The apse mosaic, in Byzantine style, is from about 820, showing Christ blessing, crowned by the Hand of God. Christ wears Roman clothes with lati clavi, a sign of high rank. He is flanked on the right by St Paul, St Cecilia, Pope Paschal I (with a miniature model of the church, identifying him as the builder and a square halo showing that he was still alive when the mosaic was made). Above Paschal I is a phoenix, a symbol of resurrection, perching on the branch of a palm tree. On Christ's left are Saints Peter, Valerian and Agatha. The figures are standing in a meadow of flowers with fruiting palm trees.