Uyuni is most likely based on Salar de Uyuni.
Salar de Uyuni (or Salar de Tunupa) is the world's largest salt flat at 10,582 square kilometers (4,086 sq mi). It is located in the Daniel Campos Province in Potosí in southwest Bolivia, near the crest of the Andes and is at an elevation of 3,656 meters (11,995 ft) above sea level.
The Salar was formed as a result of transformations between several prehistoric lakes. It is covered by a few meters of salt crust, which has an extraordinary flatness with the average elevation variations within one meter over the entire area of the Salar. The crust serves as a source of salt and covers a pool of brine, which is exceptionally rich in lithium. It contains 50 to 70% of the world's known lithium reserves, which is in the process of being extracted. The large area, clear skies, and exceptional flatness of the surface make the Salar an ideal object for calibrating the altimeters of Earth observation satellites. The Salar serves as the major transport route across the Bolivian Altiplano and is a major breeding ground for several species of flamingos. Salar de Uyuni is also a climatological transitional zone since the towering tropical cumulus congestus and cumulonimbus incus clouds that form in the eastern part of the salt flat during the summer cannot permeate beyond its drier western edges, near the Chilean border and the Atacama Desert.
The myth of the creation of the Salar de Uyuni was that Tunupa (a mountain) was a beautiful young woman, who at the time of being forced to find a husband, she chose Kusko. They lived happily during several years. When Tunupa waited for a son, a woman called Kusuna appeared and seduced Kusko. She cried and the milk of her breasts came together and fell to the floor and created the Salar.