They reside below a large mosaic of St Mark — dating from the 16th century, it likely replaced an original mosaic depicting Christ Pantocrator — who stands with his arms raised in the hemispherical lunette, looking upward toward the raised hand of God.

• The 11th century blue-clad Virgin Mary stands in the center niche, a baby Jesus in her arms, looking directly out at the viewer.
• She is flanked by eight apostles, identified by Latin inscriptions with their names. Each stands with head turned in deference toward the Virgin at the center.
• Below them, to the sides of the entrance door, are the four evangelists, arranged in canonical order from left to right: Matthew, Mark, Luke and John. In contrast to the apostles, they stand facing directly forward, a stylistic indicator of their relatively higher status. When combined, the Latin text in the arches above the evangelists’ heads offers visitors the following message, likely indirectly drawing on Isaiah 52:7-10: “These four watchmen of the church sing a sweet song that resounds throughout the heavens.”