The vault is spectacularly frescoed by the Cavalier d’Arpino. The vault has a central fresco of the Ascension of Christ, with the main arms of the cross-vaulting depicting the prophets Moses, Jeremiah, Ezechiel and Micah with Sibyls. The lunette vauls show four Doctors of the Church: Sts. Gregory the Great, Augustine, Jerome and Ambrose.

(Another photo of the center fresco here)