The Campi Flegrei caldera is a supervolcano. While a new eruption here would be more likely to result in the creation of another Vesuvius-like cone, the worst-case scenario could see it obliterating much of life in Europe. Two thousand years ago Mount Vesuvius destroyed Pompeii. Today, a larger, far more deadly supervolcano lurks on the other side of Naples. If it erupts, Campi Flegrei could wipe out...