From the Wikipedia: "The Empress Zoe mosaic on the eastern wall of the southern gallery date from the 11th century. Christ Pantocrator, clad in the dark blue robe (as is the custom in Byzantine art), is seated in the middle against a golden background, giving His blessing with the right hand and holding the Bible in His left hand. On either side of His head are the monograms IC and XC, meaning Iēsous Christos. He is flanked by Constantine IX Monomachus and Empress Zoe, both in ceremonial costumes. He is offering a purse, as symbol of the donation he made to the church, while she is holding a scroll, symbol of the donations she made. The inscription over the head of the emperor says: "Constantine, pious emperor in Christ the God, king of the Romans, Monomachus". The inscription over the head of the empress reads as follows: "Zoë, the very pious Augusta". The previous heads have been scraped off and replaced by the three present ones. Perhaps the earlier mosaic showed her first husband Romanus III Argyrus or her second husband Michael IV. Another theory is that this mosaic was made for an earlier emperor and empress, with their heads changed into the present ones."