The Lamb of God, before and after cleaning: The lamb, set before the background of a gold cross, is the central figure on the triumphal arch above the conch of the apse. The lamb’s head is turned so as to fit perfectly into its medallion frame. It is part of a Byzantine grouping known as the Deesis which also includes the Virgin Mary and John the Baptist. This Deesis is the earliest one in existence, and the only one in which Christ is depicted in the symbolic form of a lamb. All Deesis representations of Christ after 692 A.D. rendered him in human form.