On June 30th, 1908, a giant explosion flattened over 800sq miles of forest near the Tunguska river in Siberian Russia.
The area of the blast was extremely remote, but the devastation was immense. An estimated 80 million trees were flattened and whole herds of deer wiped out.
The magnitude of the blast was thousands of times greater than the nuclear bomb dropped on Hiroshima and its impact was felt as far afield as Great Britain.
Had it occurred just minutes later it would have destroyed the whole of St Petersburg and killed millions of people.