Millions of years ago, Salar de Uyuni was part of a huge prehistoric lake. Over thousands of years the water slowly dried up and left behind a thick crust of salt. In some places the salt is more than ten metres deep — that is taller than a double-decker bus standing on top of another double-decker bus.
When it rains, even a tiny bit of water spreads across the flat surface and makes it look like a giant mirror. The sky above and the ground below look exactly the same. Flamingos wade through the shallow water, and their pink reflections make the whole scene look like a painting. Some travellers say it is the most magical thing they have ever seen.
Underneath the salt there is something very special: one of the world's biggest stores of lithium, a metal used to make the batteries in phones, tablets and electric cars. The local wildlife includes flamingos, vizcachas (fluffy rabbits that look like they have long tails), and even cacti growing right out of the salt plain.
In the dry season, the hexagonal shapes in the salt crust are clearly visible — thousands of six-sided tiles stretching in every direction as far as you can see. At night, the flat surface reflects the stars so clearly that it looks as if you are floating in space.