Lake Titicaca sits 3,812 metres up in the Andes and covers more than 8,000 square kilometres. At that size it stops feeling like a mountain lake — there is a horizon, there is a swell, and the far shore is another country. It is the largest lake in South America and the highest anywhere that commercial boats still cross. It straddles the border of Peru and Bolivia on the treeless Altiplano, and drops to around 280 metres deep. The water is cold, hard blue and unnervingly clear, and the thin air makes every distance look shorter than it is. Reed beds fringe the shallow bays, and the shore is worked in small terraced plots right down to the waterline. In Andean belief this is where creation began, and the lake was sacred to the Tiwanaku long before the Inca ruled here.
The most surprising thing here is that people still live on the water itself. The Uros are a pre-Inca people who took to the lake to get away from stronger neighbours, and they build their own islands out of bundled totora reeds. Roughly 1,200 of them live on some sixty floating platforms, and the reed ground gives softly underfoot like a mattress. They pole slim reed boats with upturned prows between the islands. Further out, the terraced islands of Taquile and Amantaní rise out of the water — quiet places of stone paths and farm plots. On Taquile the men do the knitting, and the fine hats and belts they make earned the island a UNESCO listing for its weaving. Come at first light, when mist lifts off the water and the thin air turns everything sharp and still.