Fazzān (Fezzan) is one of the three historic regions of Libya, alongside Tripolitania (Ṭarābulus) in the northwest and Cyrenaica (Barqa) in the northeast. It covers approximately 550,000 square kilometres in the southwest of the country and has a population of about 440,000 (2006 census). Fazzān is part of the central Sahara and is characterised by rocky and gravely plateaux ( ḥamāda and sarīr ), wadis, and areas of sand dunes (ergs) and by the Tibesti mountains to the south. In the extremely arid climate, water can be found only in