In October 1961, the Soviet Union dropped the most powerful nuclear bomb in history over a remote island north of the Arctic Circle.

Though the bomb detonated nearly 2.5 miles (4 kilometers) above ground, the resulting shockwave stripped the island as bare and flat as a skating rink.

Onlookers saw the flash more than 600 miles (965 km) away, and felt its incredible heat within 160 miles (250 km) of Ground Zero. The bomb’s gargantuan mushroom cloud climbed to just below the edge of space.