The underground sanctuary dedicated to Saints Ephisius and Gregory the Great is organised in two parts, separated by a grille: the vestibule and the sanctuary. In the first, with a rectangular shape and barrel vault, are five busts of saints related to the Franciscan tradition. In the second room, which is equally rectangular in shape and has a barrel roof, there are several altars and polychrome stucco statuettes by Mutoni and Corbellino. The vault was decorated with tempera by Gregorio Are. The Oratory of St Michael Archangel was built between 1758-1759 following Lombard models introduced by Quallio and his assistants. The dome of the building is decorated with tempera paintings by Gregorio Are. The Convent houses a valuable collection of 17th and 18th century paintings by artists who worked in the Franciscan workshop: Antonio Todde, Giuseppe Lopez and Pietro Antonio Are.