Salar de Uyuni, Bolivia
At over 4000 square miles in area, Salar de Uyuni, located in southwest Bolivia, is the largest salt flat in the world. 40,000 years ago, the area was part of a large prehistorical lake - when it dried, two modern lakes (Poopo and Uru Uru) were left, along with 2 salt deserts. The smaller is called Salar de Coipasa and the larger is Uyuni. Salar de Uyuni is estimated to contain 10 billion tons of salt, which is mostly made of halite and gypsum.
This image of the salt flat was acquired by the MODIS on the Terra satellite on April 8, 2007.