At 4,086 square miles, Salar de Uyuni in southwest Bolivia holds the record for the largest salt flats in the world. In fact, so flat are the flats that the U.S. Geological Survey found that elevation variations across the entire area were less than one meter. It is the flattest place on the planet, and it is so stunningly featureless that you can see the curvature of the Earth there. Needless to say, this provides an opportunity to create what might be considered the planet's largest mirror, a place for the sky and earth to collide in dizzying illusions. (We wonder if the moon catches glimpses of her own reflection there.

Salar de Uyuni is part of the Altiplano of Bolivia in South America. The Altiplano is a high plateau, which was formed during uplift of the Andes mountains. The plateau includes fresh and saltwater lakes as well as salt flats and is surrounded by mountains with no drainage outlets.

The geological history of the Salar is associated with a sequential transformation between several vast lakes. Some 30,000 to 42,000 years ago, the area was part of a giant prehistoric lake, Lake Minchin. Its age was estimated from radiocarbon dating of shells from outcropping sediments and carbonate reefs and varies between reported studies. Lake Minchin (named after Juan B. Minchin of Oruro later transformed into paleolake Tauca having a maximal depth of 140 meters (460 ft), and an estimated age of 13,000 to 18,000 or 14,900 to 26,100 years, depending on the source. The youngest prehistoric lake was Coipasa, which was radiocarbon dated to 11,500 to 13,400 years ago. When it dried, it left behind two modern lakes, Poopó Lake and Uru Uru Lake, and two major salt deserts, Salar de Coipasa and the larger Salar de Uyuni. Salar de Uyuni spreads over 10,582 square kilometers (4,086 sq mi), which is roughly 100 times the size of the Bonneville Salt Flats in the United States. Lake Poopó is a neighbor of the much larger Lake Titicaca. During the wet season, Titicaca overflows and discharges into Poopó, which, in turn, floods Salar De Coipasa and Salar de Uyuni.