The 'Tsar Bomba' was tested on October 30, 1961 and is the most powerful nuclear bomb ever detonated. Developed by the Soviet Union as RDS-220, the 50-megaton hydrogen bomb was detonated in an island of the Arctic Sea. Visible from 600 miles away and capable of destroying everything within a 15-mile radius, it could deliver third-degree burns within a 64-mile radius.