The mosaics are among the finest in Rome. They are from the 12th century, but look earlier since they are in the Byzantine style, obviously still influential in Rome at the time. The appearance is dominated by the golden glow of the background, which was achieved by applying gold leaf to the backs of the clear glass tessarae used for it. At the top of the composition on the triumphal arch is the figure of Christ Pantokrator, flanked by symbols of the four Evangelists (lion, ox, man, eagle). At the bottom, Christ and the Apostles are depicted in the form of the Lamb of God flanked by a flock of twelve lambs.