When you think of nuclear disasters, you think of the Chernobyl plant in Ukraine and the Fukushima plant in Japan, and maybe Three Mile Island. But after Fukushima and Chernobyl, the third biggest nuclear disaster is called Kyshtym. Never heard of it? That’s because it happened in 1957, at the height of the Cold War, deep in the eastern Ural Mountains of the Soviet Union. The Soviets disclosed details to no one, not even the people affected. Even the name is a misdirection, because it didn’t happen in Kyshtym. It was in the town of Chelyabinsk-65 (which was renamed Ozyorsk in the early 1990s); this town, according to the Soviets, did not exist. Read about what happened there during the Cold War in an article I wrote for mental_floss.