I think this is one of the coolest things ever. We went under the city of Naples. Below the city are ancient aqueducts that reach all the way to Rome. They are also temples buried under the new city. As we ventured down the steps they talk about how during the war they used the underground city as a bomb shelter, Nuns used it to store wine under a church, and the ancient Rome it was the actual city now burried under the new Naples. They also just discover and amphitheater under all the apartment buildings. People for centuries were using it as storage or air ventilation never knowing what actually lied beneath there home.
Most of the tour was to dark to actually get any photos. But we got a few.