In 1957, a massive nuclear accident took place at the top ... and details of the devastating legacy of what is now known as the 'Kyshtym disaster' are still only just becoming clear today.

The Soviet nuclear weapons development program lagged ... In the American media, there was debate about whether the Kyshtym disaster was truly as dramatic as the defector’s account suggested.

IFL Science reports that Karachay is "the most radioactive lake on Earth". Additionally, its waters are so highly irradiated that spending just an hour sunbathing on its shores could prove fatal.