Published on Friday, April 8, 2016 by Kathy McCabe For some time, “Naples Sotteranea,” or “Underground Naples,” has been a draw for travelers from around the world. The tunnels and caverns beneath the historic Italian city are built on a porous type of rock called “tufo,” the result of centuries of hardening of volcanic ash. (The photo to the right is of an old water tunnel underneath Naples.) While muc...