The mosaic at the Altar of Transfiguration was reproduced from the last painting of the High Renaissance master Raphael. It depicts the event recorded in Matthew 17. On the top is Jesus floating between Moses and Elijah. On the bottom is the demon-possessed boy, whom the disciples failed to cure. The woman in the middle represents the church.
After Raphael died at the age of 37 in 1520, his students completed this masterpiece. It was looted by Napoleon in 1797 and returned to Italy after his defeat. It now hangs in the Vatican Museum.