Salar de Uyuni

The Salar de Uyuni is what remains of a prehistoric lake: ten thousand square kilometres of salt crust at 3,660 metres, flat to within a metre across its whole width, with islands of cactus and volcanoes at the edges. In the wet months a skin of water turns it into a mirror that removes the horizon, and 4x4s drive across it as if through the sky. In the dry months the crust hardens into hexagons and the sky is the clearest on the continent. South of it the altiplano rises to lagoons in red and green with flamingos, geysers and a pass into Chile.

What the model says

Two seasons and two different places. January to March gives the mirror and warmer nights, with rain that can flood the routes. May to October gives the dry crust, no rain at all and nights to minus twenty. The Altitude Simulator matters: arriving from La Paz at 3,600 metres is fine, arriving from sea level is not, and the southern route sleeps at 4,300 and passes 4,900. Daylight at twenty degrees south hardly moves; the cold does.

What the ground says back

The three-day crossing from San Pedro de Atacama is the way to do it, climbing through the coloured lagoons and geysers and arriving at the salt on the last morning already acclimatised. The refuges are basic and freezing, the drivers are the safety system, and the crashes that make the news have all involved speed or drink. The perspective photographs on the salt are silly and everyone does them. The sunrise on the mirror is not silly at all.

Days

Three days for the crossing, four with a buffer. Bolivia adds La Paz, the Death Road and Lake Titicaca for a fortnight at altitude, and Chile’s Atacama across the border is the natural other half.