The church's origins date to the 6th century. Later, after the Islamic conquest of Sicily, it was converted into a mosque. After the establishment of the Norman domination of southern Italy, it was returned to the Christians by Roger II of Sicily who, around 1136, entrusted it to the Benedictine monks of Saint William of Vercelli.
The church was extensively modified during the following centuries. A restoration held around 1880 attempted to restore its original medieval appearance.
The church is notable for its brilliant red domes, which show clearly the persistence of Arab influences in Sicily at the time of its reconstruction in the 12th century. In his Diary of an Idle Woman in Sicily, F. Elliot described it as "... totally oriental... it would fit well in Baghdad or Damascus". The bell tower, with four orders of arcaded loggias, is instead a typical example of Gothic architecture.
The church lies with a flank on a square construction, which was probably a former mosque. The church is on the Latin Cross plan with a nave and two aisles and three apses. Each of the square spans is surmounted by a dome. The presbytery, ending with a niche, has also a dome.
The cloister, enriched by a luxurious garden, is the best preserved part of the ancient monastery. It has notable small double columns with capitals decorated by vegetable motifs, which support ogival arches. It also includes an Arab cistern.