Lake Sarez was made in a single night. In February 1911 an earthquake in the Pamir mountains of Tajikistan dropped a mountainside onto the village of Usoi, buried it where it stood, and blocked the Murghab river with the rubble. The water backed up behind that rubble into 55 kilometres of lake. The Usoi Dam is about 567 metres high, taller than any dam engineers have ever built, and nothing about it looks built. There is no crest road, no spillway, no channel for the water to leave by. A failure would not stay local, so the dam and the lake level are watched continuously and a warning system runs down the valley.
Getting there takes you a rough drive up the Bartang Valley and then days on foot. The trail forces you across the Murghab twice, each time on a narrow cable bridge that sways underfoot above the grey meltwater, one person at a time. Those two crossings are the crux of the walk in. Most people sleep out on the barren rockfield near the crest, where there is no shelter of any kind and the temperature drops below freezing even in midsummer. Before the wind gets up you pick down the loose boulders at the base of the dam to a rocky inlet where the lake opens to its full width. Crossing the crest itself means picking a path over loose, sun-baked slide rock with the water held on one side and the empty gorge dropping away on the other. A small motorboat is the only way to cover any of the water. The walls go into the lake and keep going 500 metres below the surface, so there is nothing at the shoreline to give you scale: no beach, no trees, no buildings. Usoi went under the mountain in seconds. Sarez went under the water it trapped, a little more each year, and the lake kept the name of the village it drowned.