Piazza San Gaetano, 68, 80138 Napoli NA, Italy
Naples UndergroundNaples is a tale of two cities. Underground lies a 450 kilometer labyrinth of chambers and tunnels dating back to the 4th century B.C.E., formed when the Greeks extracted tufa stone to build ancient Neapolis. The Romans incorporated the tunnels into the city’s water system, which remained in use until the 1884 cholera epidemic, and they were later used as air-raid shelters during World War II. Guided tours are fascinating, but beware: The tunnels are narrow and dark, so they're not for claustrophobics.