The Castellaccio of Monreale or Castle of San Benedetto is the only example of a monastery - military fortress in western Sicily. The castle was built around the 12th century under William II together with the more famous Cathedral and Monastery of Monreale. It is an example of Arab-Norman architecture in Sicily. It was an integral part of a vast defense-control system of the territory following the conquest of the island from 1061 to 1072. The castle dominates the Oreto Valley and many of the limestone reliefs of the Monti di Palermo. It was probably dedicated to San Benedetto. In addition to its military function of sighting, the castellaccio was also intended as a place of rest for the monks of the nearby monastery of Monreale. An important event in the history of the castle was the attack in 1370 by Giovanni Chiaramonte's army against the Catalan nucleus supported by the Monreale monks. The clash caused damage to the structure of the castle but since the strategic position was important for the prevention of attacks from the north and south, it was essential to restore the damaged parts. In 1393 it was inhabited by King Martin I who wanted to be protected from possible attacks. Shortly after, the degradation began with the definitive abandonment which presumably occurred in the 16th century. In 1897 the monument was sold by the Municipality of Monreale to the Sicilian Alpine Club with the commitment that the latter would carry out its restoration and take care of its maintenance. In 1898 the architect Giuseppe Patricolo, an important figure in the recovery of many Sicilian architectures, dedicated himself to the recovery of the Castellaccio in its less damaged parts. After the restoration work by the Sicilian Alpine Club, the Castellaccio was reopened to the public in 1906 becoming, from that moment, an Alpine station of the Association and is one of the excursion destinations of the area. In 1996 and 2009, restoration and extraordinary maintenance works were carried out under the supervision of the Superintendency of Monuments which further allowed the usability of the north-east and north-west towers.