The town lies 568 m. above sea level in the hilly region to the right of the Salso river, at the foot of San Giuliano (727 m.) in the middle of the island. The old centre is characterized by picturesque narrow winding streets, while the modern town has been built to a neat square plan. Probably a Siculo-Greek settlement, the town was occupied by the Arabs in 829 (the name Kalat-Nissa: castle of Nissa dates back to this time) and its resultant prosperity continued under Norman rule, beginning in 1087. From then on, it shared the vicissitudes of the Kingdom of Sicily, though granted in feud by the Moncada family from the 15th to 19th century. It became part of Italy in 1860. Of interest are the Duomo (16th-17th century), the Mineralogical, Palaeontological and Sulphur-Mine Museum, the Regional Archaeological Museum, the Folklore Museum and the Civic Museum. Also of interest is the baroque Palazzo Moncada, the Palazzo Vescovile, and the ruins of Castello di Pietrarossa.
