The church retains its original splendour, which is due to the perfect balance of Byzantine, Romanesque and Muslims features. The architectural layout with aligned domes and half-barrels on the aisles was widespread in many Benedictine monastic churches in the XI century. The domes are hidden by constructions with pyramid-shaped coverings. The apse is enclosed between two soaring twin towers connected by a curtain wall decorated with entwined arches in the Arab-Sicilian style. Of the two towers, one marked the religious life of the city with the tolling of the bells, the other belonging to the Universitas was used as a watchtower.