The Apse Mosaic at San Clemente: Detail: Crucifixion
Mary and John stand left and right of the cross, which is decorated with twelve doves (for the apostles?) and planted in the leaves of the Tree of Life.
View the entire apse.
Read more about the Cross and the Crucifixion.
Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.