Naples may not be the first city on a tourist's Italian itinerary, but for people seeking underground adventure, it's a worthy stop. The draw is the sheer number of different underground tour options in various parts of the city. A tour through ancient Roman aqueducts and cisterns is one choice, while another tour visits a series of caverns and tunnels that were used over the centuries as storage spaces, hiding places, bomb shelters and underground churches. The large Fontanelle Underground Cemetery and number of ancient crypts can also be found under the city. It is also possible to head below street level to explore the more recent relics of the history of Naples, such as the bunkers and air raid shelters used during World War II.