This trail starts in Civitella del Lago, an embattled hamlet on a hilltop on the left side of the Tiber, once Todi's stronghold against attacks from the West. In 1524 this fortress was granted to the Atti family by Pope Clemens 7th, of the Medici family. The boundary wall has successively been surrounded by many other buildings, while the entrance to the castle has maintained its original pointed-arch shape. Inside the hamlet, you will find the 16th century Palazzo degli Atti. Behind the sports ground, take the uphill farm-track going eastwards; after 2.5 km you will get at a ditch. Walk on downhill along the ditch itself, as it is the main access to a 72 metre-deep karstic sink-hole, or ponor, the so-called Vorgozzo chasm ("voragine"). Walking on the same farm-track, on the left, take the mule-track going downhill to the valley of Fosso dell'Elce Barile; once in the valley, at the junction, take the other mule-track on the left, then ford the brook (two brooks meet in this point). Walk on until you get to a quadrivial crossroads; turn left on the farm-track leading to the Buche del Vento, or "Wind Hollows": they are cracks in the rock that, in particular moments of the day, blow out – or in – a powerful blast of cold air. This phenomenon is due to the presence of a deep and huge underground system beneath the rocks: the difference in temperature between the inside and the outside causes a sudden difference in pressure and thus a blast of air. Yet, up to now, nobody has found the entrance to this underground system. Follow the unsurfaced road, until at the following crossroads you take the cart-road on the right, towards Valle Spinosa; from here, another cart-road on the left will lead you back to Civitella del Lago.