In late October 1961, a Soviet plane dropped Tsar Bomba, the largest hydrogen bomb ever detonated. Now, for the first time, footage of the massive explosion is available for the public to view, Smithsonian reports.

The recently declassified Russian documentary traces the timeline of the thermonuclear weapon from its design to its historic detonation. Officially named RDS-220, Tsar Bomba was built when Cold War tensions between the Soviet Union and the United States were high. The bomb was the culmination of the race to construct the biggest and most devastating nuclear weapon on Earth.

Standing 7 feet tall and stretching nearly 26 feet long, Tsar Bomba was transported off the coast of Severny Island near the Arctic Ocean by a modified bomber aircraft. It was released with a parachute and detonated 13,000 feet above the Earth to reduce destruction on the surface. The explosion was equivalent to 50 million tons of TNT, and was 700 times as powerful as the atomic bomb dropped on Hiroshima by the U.S. The blast resulted in a 42-mile-high mushroom cloud and a flash that was reportedly visible as far as 620 miles away.

Russia’s Rosatom State Atomic Energy Corporation posted the video below to mark the 75th anniversary of Russia’s nuclear industry. After watching the footage, check out these declassified nuclear test videos from the United States government.

[h/t Smithsonian]