Shagan, Nuclear test site lake in East Kazakhstan Region, Kazakhstan

Shagan is a circular crater lake in East Kazakhstan Region that was created by an underground explosion. The water body has a diameter of approximately 430 meters and reaches depths of around 100 meters.

On 15 January 1965, a 140-kiloton device was detonated in a 178-metre-deep hole in the dry bed at the confluence of the Shagan and Ashchysu rivers, as part of the Soviet Nuclear Explosions for the National Economy programme. The blast formed a crater 400 m across and 100 m deep, with a rim 20 to 38 m high. About 20% of the radioactive products escaped and were detected over Japan, prompting US protests under the 1963 Limited Test Ban Treaty.

Locals call it "Atomic Lake" (Atom kóli) and fish there despite official warnings that the water is hazardous. The lake is part of the Balapan complex, one of the main attractions of the Semipalatinsk Test Site. In Netflix's Dark Tourist (season 1, episode 4), David Farrier swims in the lake and eats a fish from it.

The lake is located in a restricted area and access is strictly controlled, requiring special permits. Visitors should be aware that the surroundings have elevated radiation levels and protective equipment may be necessary.

Radioactive materials from the explosion dispersed far beyond the immediate area and were measured as far away as Japan. This widespread contamination made the event a subject of study for international scientists and demonstrated the global reach of nuclear weapons testing.