OTD in 1961, the Soviet Union tested the largest-ever thermonuclear bomb—a 50-Mt RDS-220 (originally designed for 100 Mt). The device, later dubbed "Tsar Bomba" in the West, was dropped by a Tu-95 Bear bomber and exploded ~13,123 feet above Novaya Zemlya inside the Arctic Circle. 
The device was 26 ft. long, 6.9 ft. in diameter, and weighed 59,525 lbs. (incl. an 1,800-lb. parachute to retard its fall). It was released above 34,000 ft. and fell for 188 seconds, allowing the aircraft time to reach a safe distance (about 30 miles). youtube.com/embed/H9AMtUey…
The 50-Megaton blast was approximately 1,570 times more powerful than the combined yield of Little Boy and Fat Man. It was 10 times more powerful than _all_ of the conventional munitions used in World War II. Although skies were cloudy, the flash was visible 621 miles away.
The fireball nearly touched the ground and the mushroom cloud rose above the stratosphere to a height of about 40 miles, seven times taller than Mount Everest. Ground-based sensors recorded the magnitude of the shockwave, which circled the Earth, at 5-5.25 on the Richter scale.
In Severny, 34 miles from ground zero, the blast destroyed every wooden and brick structure. Even hundred of miles away, wooden homes were demolished while those made of stone were damaged. Windows in buildings as far away as Finland and Norway shattered from the shockwave.
The resulting mushroom cloud grew to be 25 miles wide at its base and 59 miles wide at its top.
