Its origins, one presumes, derive from an ancient Arab village [citation needed] Located on the slopes of Mount Caputo at 310 m above sea level. The importance of Monreale is starting to be that with the advent of the Norman dynasty to the eleventh century. It was in this place where the Norman kings retired to rest from the toils of war and the government of Sicily. It was one night in 1171 that King William II the Good, had a dream the apparition revealed that the place where he had hidden a huge treasure (spoils of war of his father), with whom William was to erect a temple dedicated to her.

The king began without delay to the construction of the temple, the Archbishop's Palace and the cloister. Ordered that a hundred monks of the Abbey of Cava, headed by Abbot Theobald, their transfer to Monreale to officiate in the temple. They arrived in Monreale March 20, 1176, and the Abbot Theobald was awarded the title of "Lord of the City." On February 5, 1182, Lucio III, at the request of the same William, elevated the church of Monreale to "Metropolitan Cathedral."

First archbishop of the diocese of Monreale was between 'William the monastery of the Benedictines. At the end of the seventeenth century, the Archbishop of Monreale had 72 estates. From the elevation at the Metropolitan Cathedral today, the seat of Monreale had 54 archbishops and, among these, 14 cardinals of the Church. Even before the cathedral was finished, he spoke with wonder of the world: the same Pope Alexander III, in a note sent to the king in 1174, expressed his joy to the solemnity of the monument.

Translated from Italian with google translate

Source: Wikipedia