Beneath the city is a dense network of galleries and caves hewn out of the tufa rock. First cave dwellings, then cellars, cowsheds or warehouses for goods, the Vie Cave later became pleasant walking itineraries. Two or three metres wide and often over 15m high, some galleries spread outside the boundaries of the city walls towards the forests and surrounding countryside, as far as the Etruscan necropolises nearby. An unusual, even spectactular, promenade.