Deer drinking at a well with apostles in the vault above
In Christian iconography, the deer or hart symbolizes the Christian searching for the fountain of life, or God.
The apostles with twining vines and the ChiRho symbol for Christ
The dome
The cross is at the center while the four evangelists' symbols occupy the corners--and see below: the ox for Luke, the eagle for John, and the angel for Matthew. Not pictured is the lion for Mark.