A Tu-95V bomber dropped the bomb by parachute over the Arctic test site of Novaya Zemlya, and it exploded about 4 kilometers above the ground. Its yield of about 50 megatons made it more than 3,300 times as powerful as the Hiroshima bomb.
The weapon had been scaled down from a 100-megaton design. Two years later, the USSR and the United States signed the Limited Test Ban Treaty, which banned nuclear tests in the atmosphere.
Image: Croquant, modified by Hex, CC BY-SA 3.0, via Wikimedia Commons.
Source: Wikipedia