What is the largest salt flat on Earth?

The largest salt flat on Earth is Salar de Uyuni in southwestern Bolivia, covering approximately 10,582 square kilometres.

The salar formed when enormous prehistoric lakes on the high Altiplano gradually dried up, leaving behind layers of evaporite minerals. Its surface is covered by a remarkably level salt crust, in places several metres thick, beneath which lies lithium-rich brine. The flat’s elevation varies by less than a metre across its broad expanse, making it one of the planet’s most uniformly level natural surfaces.

During the rainy season, a thin layer of water can turn Salar de Uyuni into a giant reflective mirror. That same smoothness, along with the high-altitude clarity and bright surface, makes it valuable for calibrating Earth-observing satellites. Visitors may also see flamingos breeding in the region. Salar de Coipasa is another major Bolivian salt flat, but it is substantially smaller; Bonneville Salt Flats and Salar de Atacama are smaller still.