In 1908, a massive explosion occurred in the Tunguska region of Siberia, Russia. The explosion, which was equivalent to the detonation of around 15 megatons of TNT, flattened over 800 square miles of forest. The cause of the explosion has been the subject of much debate, with theories ranging from a meteorite impact to a UFO crash. Despite numerous investigations, the exact cause of the Tunguska event remains unknown.