The frescoes on the apse wall flanking the altar date from the church's original construction. The panel on the left of the altar shows The Manna in the Desert by Francesco Nappi, 1600. The fresco is damaged by the insertion of the coat-of-arms of Cardinal Salviati.
The “people’s altar” in front of the main altar is made from an ancient sarcophagus.
(Another photo of the fresco here)
(Another photo of the altar here)