Mount Kilimanjaro rises 5,895 metres out of the plains of northern Tanzania with no range around it, which makes it the highest point in Africa and the highest free-standing mountain on Earth. From the savanna you see all of it at once: dark forest at the base, a flat white dome above the haze, acacias and elephants in front. What no photograph shows is that the mountain stacks five climates on one slope, and the week-long walk up goes through all of them. You start in humid rainforest with monkeys moving overhead. That opens into heath, then moorland where giant groundsels and lobelias stand several metres tall on woolly stems, plants that take decades to grow and live almost nowhere else. Above them the ground turns to cold grey desert, volcanic rubble with nothing growing in it. Then ice. No rope or climbing skill is needed anywhere on the route. Some 50,000 people set out every year, and what most of them misjudge is the air rather than the ground.
High camp sits above 4,600 metres on bare volcanic gravel, with no town light within a hundred kilometres. You are awake for it anyway; the air up there breaks most people's sleep into short pieces. The last push leaves in darkness, so that you come over the crater rim at first light, ice underfoot, the plains of Africa far below under their own layer of cloud. The rim walk ends at Uhuru Peak — Swahili for freedom, the name given in 1964. The ice you are standing on is the part of the mountain that is going. About 85 percent of the summit glaciers measured in 1912 had gone by 2011, and the retreat is speeding up; what is left stands as separate blocks rather than a cap. The Chagga, who farm the wet southern slopes where most climbs begin, named the dome Kibo, their word for spotted, after the patches of snow on it. Four of the five climates will still be stacked here when the spots that named it have gone.