The frescoes from the 11th and 12th century decorate the chapels, particularly on the walls of the central stairway, in a Byzantine art style and dating to around 1200. On the south wall is a Transfiguration scene depicting Christ with Moses and Elijah, and the apostles John, James, and Saint Peter at their feet. On the archway above them are frescoes of the dove of the Holy Spirit being presented by angels, and above that Saint Lawrence and Saint Stephen holding the palm fronds that identify martyrs.