The peculiar geological nature of massive stone, on which the town of Orvieto stands, has allowed its inhabitants to excavate, in the course of 2500 years, an incredible number of grotto like caves, extending, overlapping and intersecting each other under the modern urban structure. Today, these are a precious source of historical and archaeological data. From the central Piazza Duomo, in front of the Cathedral, next to the Tourist Information Office, scheduled Guided Visits depart for the Città Sotterranea everyday. The visit in itself lasts one hour, and goes inside one of the most interesting and structured underground complexes of the town. Qualified personnel accompany the visitors, who discover the traces left by the ancient inhabitants of Orvieto, in a pathway that is easy and enjoyable. Here the effect of daylight and shadows cutting through the millenary obscurity of the subsoil unveils deep and narrow wells, along which the Etruscans followed the underground water-bearing stratum in search of water, majestic stone mills and a long series of tunnels.