The cathedral, the town's most emblematic building, is a jewel of Romanesque architecture, whose golden stone blends into that of "La Rocca" cliff. Roger II began its construction in 1131. It presents a more obvious Norman style than Palermo's cathedral: it has its full expression in the façade, finished in 1204 and flanked by square towers, and the high apse lined by small apses. The chancel has some remarkable and extremely brightly coloured mosaics.