The Salar was formed as a result of transformations between several prehistoric lakes that existed around forty thousand years ago but had all evaporated over time It is now 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. The large area, clear skies, and exceptional flatness of the surface make the Salar ideal for calibrating the altimeters of Earth observation satellites .Following rain, a thin layer of dead calm water transforms the flat into the world's largest mirror, 129 km (80 mi) across.
Salar has been used as a filming location for movies such as Star Wars: The Last Jedi , Salt and Fire (2016), The Unseen (2017), and several others.
Salar de Uyuni is a popular tourist destination, and consequently a number of hotels have been built in the area. Due to lack of conventional construction materials, many of them are almost entirely (walls, roof, furniture) built with salt blocks cut from the Salar. The first such hotel, named Palacio de Sal, was erected in 1993–1995 in the middle of the salt flat and soon became a popular tourist destination. However, its location in the center of a desert caused sanitation problems, as most waste had to be collected manually. Mismanagement caused serious environmental pollution and the hotel had to be dismantled in 2002.
Around 2007, a new hotel was built, under the name Palacio de Sal, in a new location at the eastern edge of Salar de Uyuni, 25 km away from the town of Uyuni .The sanitary system has been restructured to comply with the government regulations. The hotel has a dry sauna and a steam room, a saltwater pool and whirlpool baths.
The area has a relatively stable average temperature with a peak at 21 °C (70 °F) in November to January, and a low of 13 °C (55 °F) in June. The nights are cold all through the year, with temperatures between −9 and 5 °C (16 and 41 °F). The relative humidity is rather low and constant throughout the year at 30% to 45%. The rainfall is also low at 1 to 3 mm (0.039 to 0.118 in) per month between April and November, but it may increase up to 80 mm (3.1 in) in January. However, except for January, even in the rainy season the number of rainy days is fewer than 5 per month.
This is the best place to visit !