The mosaic in the conch here is one of the rare examples from the 7th century in Rome. The work shows the martyrs standing either side of a jewelled cross, on a golden background. They are on a green meadow, which is sprouting red roses. Over the cross is a tondo showing the Head of Christ, which may have been a later addition. At the top is a small depiction of the starry heavens, with the Hand of God the Father holding a wreath. The anonymous 16th century fresco behind the altar, below the mosaic, shows Christ and the Apostles and other saints.