Built in the same place where originally there was a Byzantine church and a first, then Muslim mosque, the construction of the Cathedral of Arab-Norman style began in 1184-1185 and has undergone numerous interventions over time. The porch in Catalan-Gothic style in 1453 finely decorated, is composed of three arches closed by two towers, the first column on the left is clearly visible inscription Koranic portal masterfully carved from Gambara dates back to 1400, and is a combination of Gothic, Baroque and Norman, though the most radical were carried out by Ferdinando Fuga in late '700 and early '800, who erected the dome uneven compared to the rest of the building and destroy the side walls and wooden ceiling. Of great importance to the inside on the left side, the tombs of the Norman kings Roger II, daughter of Constance of Altavilla mother of Frederick II and the latter and his wife Constance of Aragon, to the right of the altar of Santa Rosalia the relics of the patron saint of the city enclosed in a silver casket, to the right of this you can access the treasure of the cathedral full of chalices, monstrance and the beautiful crown of Constance of Altavilla. Of great importance also the crypt which houses the tombs of the bishops and of the Norman kings.