Sukhoy Nos (meaning "dry cape") is the easternmost point of the north island of Novaya Zemlya (meaning "New land") archipelago in the Barentz sea north of the European part of Russia. It is a barren and inhospitable land, with freezing temperatures during the whole year. But more importantly - it was one of the places where the former Soviet Union used to test their nuclear weapons. It was also the place, where the largest and strongest bomb ever built - the Soviet hydrogen "Tsar Bomba" was detonated.
So, in 1961 USSR and USA were pretty much trying to show each other how great their arms were. So Khrushtchev went as far as to speculate the creation of nuclear bombs with 100 Mt yield. However, luckily for all of us, only the testing of a bomb with 50 Mt yield was finally ordered. For comparison- the yield of the nuclear bomb that ruined Hiroshima was 16 kt or 300 times less.
So, on October 30, 1960 a specially modified Tu-95V plane with removed fuel tanks and bomb-dropping doors carried the bomb to the Sukhoy Nos testing spot. The bomb weighed 27 tons and was 8 m(26 ft) long by 2 m (6.6 ft) in diameter and it was attached to 800 kg parachute. It was dropped from an altitude of 10.5 km (6.5 mi); it
was designed to detonate at around of 4 km (2.5 mi) over the surface. It detonated at 11.32.
The explosion was so giant that the bomb produced a fireball 8km (5mi) in diameter, it was seen from a 1000 km away. The rocks around the site were melted and still can be seen on the satelite photos. The mushroom cloud was 64 km (40 mi) high. Its shockwave was felt all around the northern shores of Russia.. It broke wooden houses, roofs, doors and glass windows as far away as Norway and Finland. Were it detonated on the ground it would have caused a 7.1 magnitude earthquake.
The bomb was deemed impractically powerful and the USSR never built a second one. Then, in 1963 USSR and USA and UK signed the Partial Nuclear Test Ban treaty prohibiting testing of nuclear weapons
except underground, because to stop the excessive release of nuclear fallout in the atmosphere. So until 1990 nuclear detonations in Novaya Zemlya were done only underground at another test sites and and in 1990 nuclear testing at the place stopped altogether.
Approximate Coordinates of the detonation spot:73° 48′ 26″ N, 54° 58′ 54″ E
Video of the explosion