The lunette above the altar has a large fresco by the Cavaliere d'Arpino of The Vision of St Gregory Thaumaturgus. Our Lady and St John the Evangelist are at the left. This is historically the first instance of a vision of Our Lady to a private person on record. The vault has St Luke by the Cavaliere in the middle, and the two side frescoes are works by Domenico Corvi. SS Irenaeus and Cyprian are on the right, and SS Ignatius of Antioch and Theophilus of Antioch on the left.