Orvieto lies in the south-western part of Umbria, in the province of Terni, bordering on the province of Viterbo in Lazio. Orvieto is set on a tuff-stone cliff at an altitude of 325 meters, dominating the valley below where the Paglia and Chiani rivers run before flowing into the river Tiber. This enormous platform in brown, volcanic tuff stone, rising from twenty to fifty meters from the countryside, was created by eruptions of some volcanos, that deposited an enormous quantity of material. The highest point is Mount Peglia (837 metres) near the town of San Venanzo. The territory of Orvieto is part of the Mount Peglia and Selva di Meana Mountain Community and part of it lies in the Tiber River Park, a regional park of Umbria created as a WWF protected area in 1990. It is seat of the "City of Orvieto" Study Center Foundation -University, Research, Higher Education.