Semipalatinsk Test Site

The Semipalatinsk Test Site (STS or Semipalatinsk-21), also known as "The Polygon", was the primary testing venue for the Soviet Union's nuclear weapons. It is located on the steppe in northeast Kazakhstan (then the Kazakh SSR), south of the valley of the Irtysh River. The scientific buildings for the test site were located around 150 km (93 mi) west of the town of Semipalatinsk (later renamed Semey), near the border of East Kazakhstan Region and Pavlodar Region with most of the nuclear tests taking place at various sites further to the west and south, some as far as into Karagandy Region.
The Soviet Union conducted 456 nuclear tests at Semipalatinsk from 1949 until 1989 with little regard for their effect on the local people or environment. The full impact of radiation exposure was hidden for many years by Soviet authorities and has only come to light since the test site closed in 1991.From 1996 to 2012, a secret joint operation of Kazakh, Russian, and U.S. nuclear scientists and engineers secured the waste plutonium in the tunnels of the mountains.Since its closure, the STS has become the best-researched atomic testing site in the world, and the only one in the world open to the public.