There has never been anything quite like it.
On June 30, 1908, something – we still don’t know what – streaked across the skies of Siberia, and exploded in the vicinity of Tunguska. At that time, Siberia was even more wild and uninhabited than it now is. The nearest witnesses were miles away, and most of the world remained blissfully unaware that anything had happened there.
But in 1920, Russian scientists began an investigation of the site that is still going on. They have discovered that the event was mostly likely a meteor that detonated in the air above Tunguska, devastating the taiga for miles in every direction in a manner very similar to that of a large thermonuclear explosion. If the course of the object had varied by only a few degrees, it might easily have hit somewhere else, where the damage and loss of life would have been considerably greater. As it is, there were no known deaths – although records, particularly of the nomadic Evenki people who lived in the region at that time, were not well-maintained.
Theories abound as to what might have caused the enormous explosion, and it says something that the crash-landing of alien spaceship is one of the tamer ones.