Lake Sarez did not exist until February 1911, when an earthquake shook a mountainside loose and sent it crashing onto the village of Usoi, burying the settlement and damming the Murghab River under more than two cubic kilometres of rock. The debris pile it left, the Usoi Dam, rises about 567 metres above the old riverbed — taller than any dam ever built, natural or engineered. Behind it the river backed up over the following years into a turquoise lake more than 55 kilometres long and over 500 metres deep, its surface sitting above 3,200 metres and hemmed on every side by glaciated Pamir peaks that climb well past 5,000 metres. The dam is still nothing but loose rubble, and it is watched around the clock for any sign that it might one day give way.
Reaching the lake is a serious undertaking: a rough drive up the Bartang Valley, then a long trek along exposed, rockslide-scarred trail — crossing the Murghab twice on swaying cable bridges — to a lonely monitoring station on the shore. The reward is a scale that photographs never quite hold: glassy turquoise water pinned between bare rock walls and snow summits, the silence broken only by wind and the drone of a small motorboat. Most visitors camp on the barren rockfield near the dam crest before a small boat carries them out at dawn onto water that, by volume, could fill a small sea. Even now Sarez is one of the least-visited great lakes on Earth: reaching it needs a special permit on top of the standard Gorno-Badakhshan travel permit, a licensed guide, and a narrow summer window when the passes are open.