The Cathedral of Monreale (Italian: Duomo di Monreale) is a church in Monreale, Metropolitan City of Palermo, Sicily, southern Italy. One of the greatest existent examples of Norman architecture, it was begun in 1174 by William II of Sicily. In 1182 the church, dedicated to the Nativity of the Virgin Mary, was, by a bull of Pope Lucius III, elevated to the rank of a metropolitan cathedral. Since 2015 it is part of the Arab-Norman Palermo and the Cathedral Churches of Cefalù and Monreale UNESCO Heritage site.

source : wikipedia