The layout of many central Italy cities is characterized by the presence of historical buildings but the more than bi-millenary frequentation of many of these sites requires further investigation to determine whether the grid can be referred to pre-medieval organization. The two principal approaches to the problem involve either large scale excavations or an investigation based on the geological nature of a site where underground structures that were functional to the city above were examined. It is the second of these alternatives that applies in particular to inner and southern Etruria since these areas are characterized by soft tuff or tufa stone plateaux. The paper analyzes the situation in the city of Orvieto-Volsinii-Velzna in Umbria, where as early as the 19th century Count Adolfo Cozza proposed an interpretation of Etruscan tunnel and cistern complexes as a system that played a functional role in the layout of the streets and buildings. More recent studies have considerably in creased our knowledge of features connected to the management of water resources, subsequently ignored in the Late Antique and Medieval settlements.
