The small town of Uyuni, in the Potosí Department in south western Bolivia, was founded in 1890 as a trading post. It is 240 kilometres south west of Potosí and lies at 3,670 metres above sea level at the edge of a large plain, with the world's largest salt flats, the Salar de Uyuni, nearby. Uyuni is a railway junction, has a population of around 10,000 people, an extensive street-market and, uniquely, a "train cemetery" with old, rusting steam locomotives.
Salar de Uyuni (also called Salar de Tunupa) is the world's largest salt flat with an area of around 11,000 km² at an altitude of 3,650 metres. The area was part of Lake Minchin, a giant prehistoric lake, around 40,000 years ago. When eventually the lake dried up, it left behind two modern lakes, Lago Poopó and Lago Uru Uru, and two major salt deserts: Salar de Coipasa and the larger Salar de Uyuni.
Salar de Uyuni is estimated to contain 10 billion tons of salt, of which less than 25,000 tons is extracted annually, with pick and shovel. The salt lake is also a breeding ground for three species of South American flamingos. There are tracks that connect settlements around it and several "islands", like Isla de Pescadores, with its stands of cactus. One of the highlights is the unique Hotel Luna Salada, built entirely out of salt blocks, inside and out. Various travel companies offer trips by four wheel drive around the area.