Chacaltaya (5,421 m)

The minibus takes you up to 5,250 metres and the rest — thirty to sixty minutes on foot — is down to you: that is how you climb Chacaltaya from La Paz. No technique, no previous experience, nothing but breathing slowly and accepting the pace the air imposes, which will strike you as ridiculous. You reach 5,421 metres slowly, and that slowness is part of the thing.

Before that comes a road that gains height so fast the body does not get to argue with it. In a little over an hour the minibus leaves the city, crosses the altiplano and stops at Milluni, where the coca tea arrives hot with whole leaves floating in it. You are still comfortable; the landscape still looks like something you know. Then the world starts emptying out: the trees go, then the shrubs, then the grass. What is left is dark ochre rock, patches of old snow in the hollows and a sky that gets bluer and bluer, almost black straight above your head.

The moment is when you open the door and step out. You take a breath, and the air comes in but does not fill you. It does not hurt and it is not frightening: there is simply less of it. You take three steps to the edge of the platform and your heart answers as though you had been running. For a lot of people this is the first time 5,250 metres stop being a number and become a sensation in the chest, and that stays with you. And only then do you look around. There is the Club Andino Boliviano refuge, a low building worn down by wind, dating from 1939 — the same year as the ski lift installed here, the first in South America. For decades this was the highest ski resort in the world. The glacier that held it up was around 18,000 years old and covered 0.22 km² in 1940; by 2009 there was nothing left, and it melted faster than any projection had anticipated. It needs no soundtrack: the numbers are enough. On that same slope, at 5,220 metres, the Cosmic Physics Laboratory of the Universidad Mayor de San Andrés has been running since the 1940s, put here for a simple reason: at this height there is less atmosphere overhead and the particles arriving from space read more clearly. In 1947 and 1948 this mountain held the photographic plates behind the work that confirmed the existence of the pion — the research that took the 1950 Nobel Prize in Physics. It is a plain building, with no ornament. Part of the matter of the universe was read there.

Then come the thirty to sixty minutes to the top: three steps, pause, three steps, pause, all the way to 5,421. Up there the horizon opens right around: Huayna Potosí on one side, massive and white, at 6,088 metres; Illimani on the other, further off, at 6,438, the highest in the Cordillera Real. Below, the altiplano stretches out flat and brown until it runs out, and La Paz shows up as a grey smudge tucked into its hollow, so small it is hard to believe you were inside it this morning. On the clear days of June to September, to the west, you can pick out a line of a different blue from the sky: that is Lake Titicaca. Nobody stays long up there — the cold and the wind see to that — but it is more than enough, and the way down gives everything back at once: dense air, noise, the city.

Before you book: a minimum of 48 h acclimatising in La Paz is required (condition of sale); the driver specialises in high-mountain routes and, at any sign of feeling unwell, the descent to lower altitude is immediate. Not suitable for children under 10, during pregnancy, or with heart problems or uncontrolled high blood pressure, significant vertigo or very limited fitness; if you have any doubts, talk to a health professional before booking. The light snack with water that is included is exactly that, a snack: it is not a full lunch.

Rates per person — from USD 48.

Want to add Valle de la Luna to the same day? See Chacaltaya + Moon Valley
Looking for a tougher high-altitude walk? See Laguna Charquini