Salar de Uyuni

Salar de Uyuni (or Salar de Tunupa) is the world's largest salt flat. It is over in area. 
It is in Potosí in southwest Bolivia, near the crest of the Andes at an height of 3,656 metres (11,995 ft) above sea level.
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. The large area, clear skies, and exceptional flatness of the surface make the Salar ideal for calibrating the altimeters of Earth observation satellites.