Salar de Uyuni is the world's largest salt flat at 10,582 km² (4,085 square miles). It is located in the Potosí and Oruro departments in southwest Bolivia, near the crest of the Andes, 3,650 meters high. When it is covered with water, the Salar de Uyuni reflects the sky.
The salt is over 10 meters thick in the center. In the dry season, the salt planes are a completely flat expanse of dry salt, but in the wet season, it is covered with a thin sheet of water which makes the most beautiful reflections.
Salar de Uyuni is estimated to contain 10 billion tons of salt, of which less than 25,000 tons is extracted annually.
You can see every mountain and every cloud reflected in the salar and you can't tell how far away they are or where the sky starts and ends.
Due to its large size, smooth surface, high surface reflectivity when covered with shallow water, and minimal elevation deviation, Salar de Uyuni makes an ideal target for the testing and calibration of remote sensing instruments on orbiting satellites used to study the Earth.
In addition to providing an excellent target surface the skies above Salar de Uyuni are so clear, and the air so dry, that the surface works up to five times better for satellite calibration than using the surface of the ocean.
