I heard of one that actually detonated over Siberia, in the 20's or 30's I think. Flattened hundreds of square miles of timber. Preety cool, unless you're under it.
That was the famous Tunguska explosion in 1908, probably caused by a fragile meteor or comet that overheating during entry into the Earth's atmosphere and exploded with the force of a 15-megaton thermonuclear bomb at relatively low altitude. That was the reason why strong blast effects were recorded as much as 50 miles away from the point of the blast.