The church was founded in the 8C to house the relics of Saint Gregory, by a group of nuns who were fleeing the Byzantine persecution. The interior is in a totally exuberant, Baroque style. You can admire the frescoes of Luca Giordano which decorate the single nave and the cupola. The ceiling is covered by 16C gilded woodwork. In the cloister, you can admire an 18C fountain representing Christ and the Good Samaritan.