In the conch of the apse there is a important mosaic of the Madonna and Child between the apostles James, John, Peter and Andrew. This probably dates from Pope Alexander’s restoration to 1161. The Hand of God holding a wreath is above Our Lady, and the figures are within an arcade of arches which is a figurative representation of a palace. The archivolt of the triumphal arch has flowers and fruit with the Chi-Rho monogram at the top.

(Another photo of Madonna here)