Mustang (from Tibetan Mun Tan (Wylie smon-thang) which means fertile plain) is the former Kingdom of Lo and now part of Nepal, in the north-central part of that country, bordering Tibet on the Central Asian plateau between the Nepalese provinces of Dolpo and Manang. The Kingdom of Lo, the traditional Mustang region, and "Upper Mustang" are one and the same, comprising the northern two-thirds of the present-day Nepalese Mustang District, and are well marked by official "Mustang" border signs just north of Kagbeni where a police post checks permits for non-Nepalese seeking to enter the region, and at Gyu La (pass) east of Kagbeni.
Upper Mustang is located north of Annapurna and at an average altitude of 4,000m is geologically and culturally part of the Tibetan plateau. The valleys are arid and dry with colourful rock formations containing many cave dwellings high up in the cliffs. The first trekking parties were allowed into Upper Mustang in 1992 and there are still very few people (about 700 trekkers each year) visiting Upper Mustang as a result it is one of the few places left where one can see undisturbed Tibetan culture.