The main feature in the apse is Christ in Majesty (orMaiestas Domini), on the vault. He appears inscribed inside the mandorla, wearing the cruciferous halo and dressed in a tunic and cloak, drawn with very stiff creases and with motifs imitating precious stones at the edges. He is making the habitual gesture of blessing with his right hand while with his left hand he presents the book, which is closed. Clearly frontal in nature, he is seated on the arc of heaven and rests his feet on a small arc, also depicted as an imitation of luxury items. Alpha and Omega are inscribed on either side.The vault is completed with the Tetramorph, with the four beings that symbolize the evangelists arranged centrifugally. The crudeness of the drawing is evident, especially in the lion of Mark; this has occasionally led it to be mistaken for a bear. The inscription, however, identifies it beyond a shadow of a doubt with the evangelist. Completing the composition is a cherub, on the left, and a seraph, on the right, identified by the corresponding abbreviated inscriptions. They are thurifer angels, so they are swinging the corresponding thuribles, drawn between the figures and the mandorla. At the sides we see the advocate archangels, intercessors between God and mankind: Michael on the left and Gabriel on the right.On the wall or semi-cylinder, partially conserved, Mary appears with the Apostles, who include Saint Paul. The left-hand part has in fact almost completely disappeared. All the figures are shown standing and from the front, against a background of plain coloured bands. On either side of the window in the middle, Mary used to appear on the left - only part of her head can be seen - while Saint Paul appears on the right. He can be distinguished because of a wrongly interpreted bald patch and he is holding a cup in his left hand, with which he possibly evokes his condition as Christ's chosen instrument, according to the Biblical text (Acts of the Apostles, 9:15). Next to him, some of the Apostles are depicted: Saint John, Saint Bartholomew and, on the other side of the south window, Saint Thomas and Saint Barnabas, according to the inscriptions that identify them.On the lower register, there are curtains painted yellow, with depictions of plants, from which hang horns and chalices. The separation between it and the wall is marked by a border of meanders.