Nothing lives in Tilicho Lake. There are no fish in it and not even plankton, which is unusual enough that people go days out of their way to look at the water. It lies at 4,919 metres in the Annapurna range of central Nepal, directly under the 7,134-metre wall of Tilicho Peak, and that wall is where the water comes from. Ice grinds off it, fills a bowl of bare rock and scree, and the cold keeps everything else out. The lake is a side trip off the Annapurna Circuit, and the walk is the part people remember. It leaves the main trail at Manang, a district of old villages built of stacked stone, with carved prayer walls, flat roofs and yak trains in the lanes, where you give up a day to let your body catch up with the height. Beyond the village of Khangsar the path crosses a notorious slope of loose scree and shifting rock above a long drop, taken in the frozen hours of the early morning while the ground still holds.
Below base camp the valley opens into grazing meadows, with yak herds moving between glacial ponds and herders' stone shelters on the slopes. The last climb to the shore is short and punishing. It tops out near 4,900 metres, and in that air you stop every few steps. Then you crest the ridge into near-total silence, with prayer flags snapping along the shore. The water is a hard blue-green that shifts with the light, and nothing moves on it. Hindus know this as the Kak Bhusundi lake of the Ramayana, where a crow-sage first told the story of Rama to Garuda, the king of birds, and pilgrims still climb up for that. In 2000 three Russian divers carried tanks to the shore and went down into the freezing water, in what stood for years as the highest-altitude dive ever made. They surfaced having seen the bottom, and the bottom was as empty as the surface.