A magnificent cathedral, in northwestern Sicily, Italy, constructed between 1174-1189 by William II, the third Norman king of Sicily. Little now remains of the monastic buildings except the splendid cloister (with 216 marble columns) adjacent to the cathedral. The cathedral is one of the richest and most beautiful churches in Italy, combining Norman, Byzantine, Italian, and Saracen styles. Particularly notable is the interior mosaic decoration, one of the largest in existence. The subjects of the mosaics include an Old Testament cycle, the miracles of Christ, the life of Christ, and the lives of the saints Peter and Paul. It was created by a group of craftsmen trained in Byzantium.