Orvieto stands on a tuff overlooking the valley of the river Paglia, right tributary of the Tiber, and just below the city receives from the left Chiani, Chiana Romana from the Valdichiana. This enormous mesa tufa, which rises from twenty to fifty meters from the level of the campaign, is due to the collapse of ground Sourge (clouds and glowing avalanches) by Quaternary volcanoes system Volsinio, wreck in the caldera which hosts the largest volcanic lake Europe, that of Bolsena.
The archaeological evidence of Etruscan, provided by excavations and studies in recent years, offer a fairly reliable, although still incomplete, the ancient city, identified after many uncertainties and controversies between etruscologi, in the city of Velzna, one of twelve Etruscan city-states. Called by the Romans "Volsinii" stood near a famous Etruscan sanctuary, Fanum Voltumnae, visited each year of the inhabitants of Etruria that flowed to celebrate religious rites, games and events. The city had, from the eighth to the sixth century BC, a remarkable economic development, which mainly benefited wealthy families in a strongly oligarchic regime, and a population increase, in the composition of the population, shows an openness to a multiethnic city; everything you have feedback from the remains of the city on the cliff and mainly from the nearby necropolis. The city reached its peak between the sixth and fourth centuries BC, becoming a thriving commercial and artistic, with a military supremacy guaranteed by its strategic position which gave her the appearance of a natural fortress.