The Vision of St Gregory was painted on the vault in 1630 by Girolamo Nanni and Francesco Nappi. The subject is the liberation of souls from Purgatory through the prayers of the faithful and the intercession of saints St Gregory the Great and St Bernard of Clairvaux. To the left is the monument of Cardinal Gerolamo Souchier (1571), and to the right, that of Pompeo Cornazzano, bishop of Parma (1647).