Salar de Uyuni, located near the small town of Uyuni in southwest Bolivia, is the world's largest salt flat, nearly 250 kilometers long from east to west, and 100 kilometers wide from north to south, covering an area of about 10,582 square kilometers.  Salar de Uyuni has an estimated reserve of 10 billion tons of salt.  Moreover，its large area, clear skies and exceptional surface flatness make the Salar de Uyuni an ideal object for calibrating the altimeters of the earth observation satellites.

Every winter, filled with rain water, the salt flat turns into a shallow lake; while in the summer time, the lake dries up leaving behind a layer of salt crust with the centre section as thick as 6 meters, hard enough for people to drive across the surface of the lake.  After it rains, the lake surface is like a mirror, reflecting the blue sky and the clear white clouds, truly the legendary "Mirror of the Sky".

Some 40,000 years ago the region was covered by a giant salt lake.  At some point the lake dried up, leaving behind a salt flat in the shape of a crescent moon.  The boundless salt flat is also a sanctuary for pink flamingos and about 80 species of rare birds.  Surprisingly, some hotels are completely built with salt bricks.  The singularly beautiful natural scenery and the serenity makes Salar de Uyuni a dreamland for tourists all over the world.

Source：
http://en.wikipedia.org/wiki/Salar_de_Uyuni
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