Upper Mustang is situated of the Trans Himalayan region of Nepal refers to the arid Tibet-like region at the northern end of the Kali Gandaki (which is simply known to its inhabitants as Lo). Mustang is probably a Nepalese mispronunciation of the name of the capital of Lo, the city of Manthang. The name is pronounced "Moo-stang" and has nothing to do with either the automobile or horse with a similar name. Officially, Mustang is the name of the district along the Kali Gandaki from the Tibetan border south to Ghasa. The capital of the Mustang district is Jomsom; the region of Tibetan influence north of Kagbeni is generally referred to as upper Mustang. Upper Mustang consists of two distinct regions: the southern region, with five villages inhabited by people related to the Manangis; and the northern region (the ancient kingdom of Lo where the language, culture and traditions are almost purely Tibetan. The capital of Lo is named Manthang, which translates from the Tibetan as "plain of aspiration". Many texts refer to the capital as Lo Manthang, but this is not strictly correct.
Other texts spell the name of the kingdom as Lho, but this is a transliteration of the Tibetan word for "south" and is also incorrect. Thus the portion of the upper Mustang district north of Samar is Lo and its capital is Manthang. The king of Lo is the Lo Gyelbu, though most people use the Nepalese term raja. To avoid total confusion with existing maps and texts, this page refers to the capital of Lo as "Lo Manthang". Because of the cold and snow, most of the population departs from Lo on trading expeditions during the winter. That's the reason trek season starts from late March until at the end of October. The trek does not go to extremely high elevations, but the cold, dust and unrelenting afternoon winds can make the trek less pleasant than other treks in Nepal. Because of the wind and the lack of water, you must always camp in a village, but these are not conveniently spaced, so some days are quiet short and others are long. There are several other routes connected with this region trekking, please find some sample routes as given here.