Tilicho Lake holds 156 million litres of glacial meltwater in which nothing lives — no fish, not even plankton, have ever been recorded here. It sits at roughly 4,919 metres in Nepal's Annapurna range, fed by glaciers spilling off Tilicho Peak, a 7,134-metre wall standing directly above; the fine rock flour they grind and carry down is what turns the surface the deep turquoise and indigo that shift with the light. Four kilometres long and about 85 metres deep, the lake was for years regarded as the highest of its size on Earth, until Kajin Sara, higher still in the nearby Nar-Phu valley, quietly took the title. For much of the year it lies frozen or scattered with ice floes, ringed by bare rock and snow with nothing green in sight.
Getting here is the hard part. From the stone village of Khangsar the trail leaves the Annapurna Circuit and crosses a notorious slope of loose scree and shifting rock, an exposed stretch where trekkers pick each step above a long drop, before reaching Tilicho Base Camp at 4,150 metres. The final push is short but punishing in the thin air; when you crest the ridge, the whole basin of turquoise water opens below the peaks in near-total silence. Prayer flags snap along the shore, the white summits stand mirrored on calm mornings, and the effort of the climb settles into something quieter. Hindus hold this to be the Kak Bhusundi lake of the Ramayana, and it is easy to understand why a place this remote and this still gathered its stories. Come at dawn, before cloud boils up off the ridges, and the first light fills the water with colour.