Salar de Uyuni: Bolivia's Vast Salt Flat Explained

What is Salar de Uyuni?

Salar de Uyuni is a broad plain covered with salt in the southwest of Bolivia ¹. Records place it in Oruro Department and Potosí Department ². In Spanish, salar means a place covered with salt ¹.

Its area is about 10,582 square kilometres ². Sources call it the biggest salt flat on Earth ¹. It lies very high up, at 3,661 m ².

A hard salt crust sits above very salty water ¹. That water holds dissolved forms of sodium, lithium and magnesium ¹. In places the salt is around 8 meters deep, and the land stays almost level from edge to edge ¹.

How did it form?

The flat belongs to a high tableland in Bolivia called the Altiplano ¹. This tableland rose with the Andes mountains ¹. Water there has no outlet to the sea, so lakes filled and then dried ¹.

Between about 30,000 and 42,000 years ago, this zone held a huge early lake named Lake Minchin ¹. Over time it gave way to Paleo Lake Tauca, then to a more recent lake named Coipasa ¹. Coipasa is placed at 11,500 to 13,400 years ago ¹.

As Coipasa dried, it left two present-day lakes plus two salty plains, Salar de Coipasa and the bigger Salar de Uyuni ¹. Beneath Uyuni today is lake mud mixed with salt and soaked in brine ¹. Small islands near the middle are old volcanic peaks that once stood above or within the early lake waters ¹.

What makes it special, and when should you visit?

The wide, level ground and clear skies help teams check height tools on satellites that watch Earth ¹. The flat is also a crossing route over the high plateau and a breeding site for several flamingo kinds ¹. The water below holds much lithium ¹.

Visitors often come for the reflections. When light rain leaves shallow still water, the sky reflects so fully that the area is called the largest mirror in the world, about 129 km across ¹. The name Uyuni comes from an Aymara word for an enclosed space ¹. A town also named Uyuni is a starting point for trips ¹.

As of October 3, 2026, days are mild and nights are cold through the year ¹. Daytime highs are near 21 degrees Celsius from November to January, and near 13 degrees in June ¹. Night lows fall between minus 9 and 5 degrees ¹. Monthly rain is often only 1 to 3 mm from April to November, but can reach 80 mm in January ¹. Rainy days are often under five per month, except in January ¹. In plain terms, drier months suit travel and salt patterns, while wetter months suit reflections, but local conditions vary.