The Orvieto comune has opened some of the tunnels under the city, with guided tours providing a taster of the vast network honeycombing the tufo subsoil (15m/45 ft. below the surface). The visit can be overly didactic, but you do get to see an underground 14th-century olive press (the constant temperature of 14°C was great for oil making). You can also peer down a few claustrophobically narrow Etruscan-era wells, wander around a subterranean quarry for pozzolano (a volcanic stone powdered to make cement mix) in use as late as the 19th century, and tour a series of Etruscan pigeon coops (no, seriously) carved out of the cliff-side rock. Note that the tour involves a steep climb up and down 55 steps, along a narrow rock-hewn passage.