Salar de Uyuni Mirror Effect: Bolivia's Salt Flat Where Sky Meets Ground

After the rains, Bolivia's Salar de Uyuni becomes the largest mirror on Earth. A few centimetres of still water spread across 10,582 square kilometres of salt, the horizon disappears, and clouds seem to float both above and below the people walking across it. This is the world's largest salt flat, high in the Andes at about 3,656 metres above sea level.

A traveller reflected in shallow water on Salar de Uyuni with distant mountains behind.

How the Salar de Uyuni mirror effect works

The secret is flatness. Across the whole salar, the height of the surface varies by less than one metre. When rain falls in the austral summer, a thin, even sheet of water settles on the crust instead of draining away, creating a reflective surface that can stretch for around 129 kilometres. On a windless day it repeats the sky so perfectly that the eye loses track of where the ground ends.

The same qualities make the salar useful to science. Its flatness, clear skies and bright white surface make it one of the main calibration sites for satellite altimeters and sensors used by NASA, ESA and other agencies.

Salar de Uyuni mirror surface – photo Alamy — Photo: Alamy

White clouds mirrored across the water-covered salt flat at Salar de Uyuni.

How the world's largest salt flat formed

Salar de Uyuni is what remains of a chain of prehistoric lakes on the Altiplano. Lake Minchin covered the area roughly 30,000 to 42,000 years ago; its successor, Paleo Lake Tauca, was about 140 metres deep. As the climate dried, the water evaporated and left behind Salar de Uyuni and the smaller Salar de Coipasa.

The salt crust ranges from tens of centimetres to several metres thick. Underneath lies a brine rich in sodium, potassium, magnesium and lithium. Bolivia holds about 22% of the world's known lithium resources, most of them beneath the salar, and Landsat images published by NASA show a lithium plant with lined evaporation ponds growing on the salar between 2013 and 2019.

Salar de Uyuni – photo Corbis — Photo: Corbis

Reflections on Bolivia's salt flat – photo Alamy — Photo: Alamy

Salar de Uyuni landscape – photo Alamy — Photo: Alamy

Things to see on and around the salar

Incahuasi Island: a rocky outcrop in the middle of the salt, covered with giant cacti and home to viscachas.
Flamingos: Chilean, Andean and James's flamingos breed here each November.
Salt hotels: several hotels are built largely from salt blocks, including one on the eastern edge, about 25 kilometres from Uyuni.
Train cemetery: about 3 kilometres outside Uyuni town, rusting locomotives from the railways built in the late 1800s to carry minerals to Pacific ports.

Salar de Uyuni after rain – photo Alamy — Photo: Alamy

Sky reflected on the Uyuni salt flat in Bolivia

Salar de Uyuni horizon – photo Corbis — Photo: Corbis

Best time to visit and photography tips

For the mirror, go in the rainy season. Rain is scarce from April to November, at about 1–3 mm a month, and peaks in January at up to 80 mm, so December to March gives the best chance of standing water. In the dry months the surface turns into a bright white plain of hexagonal salt patterns, ideal for the famous forced-perspective photos where a friend appears to stand on your hand.

The town of Uyuni is the gateway, and most visitors join a jeep tour of one to several days. Nights are cold all year at this altitude, so pack warm layers, strong sun protection and sunglasses for the glare. Wrap cameras against salty splashes and give yourself a day or two to adjust to the altitude before long days out on the flat.

Our Salar de Uyuni travel guide covers more planning choices, and Bolivia through travel photography shows the country's other landscapes. For more fun with scale, see our perspective photography ideas.