This damn interesting article from damninteresting.com describes the largest bomb ever built — the USSR’s Tsar Bomb.
The giant fireball reached from ground-level to about 34,000 feet into the air, violently releasing 3800 times more explosive energy than the Hiroshima bomb– equivalent to fifty million metric tons of TNT. One hundred kilometers from ground zero the heat would have inflicted third degree burns. Atmospheric focusing produced areas of destruction hundreds of kilometers from ground zero, including wooden structures which were completely destroyed, and some shattered windows in Finland. The explosion’s atmospheric shockwave traveled around the Earth three times before it dissipated.
Video footage of the bomb with appropriately frightening music is available here.






