Reporter: Allison Langdon
Producer: Gareth Harvey
Mountains aren't usually known for their role in making and preserving history.
But when Mount Vesuvius erupted two thousand years ago - it did just that.
The volcano's downpour of ash was so quick it destroyed the ancient city of Pompeii and caught its people in a moment in time.
However, the destructive power of Vesuvius is not consigned to the history books.
Today it threatens the city of Naples, which is home to three million Italians.
They know that when Vesuvius next explodes, there will be very little warning.