The big fresco of the apsidal calotte, with the benedictory Redeemer in the middle, reproduces the cycle of the Legend of the true Cross. Although reduced, it's referred to the Legenda aurea by Jacopo da Varazze(XIII cent.).
It has been traditionally attributed to the Pinturicchio or the Perugino but now, after the restoration, to Antoniazzo Romano and fellows (in the end of the XV cent.).
The two frescoes at the sides of the apse, encircled by golden frames of plaster, are by Corrado Giaquinto(1699-1765).
On the right: "Moses makes water gush from the cliff" (The Book of Numbers 20, 7-11)
On the left: "The bronze snake"(The Book of Numbers 21, 6-9)