The city of Orvieto exists in symbiosis with the tuff cliff on which it stands, an extraordinary example of the integration of nature by the work of man. An example of the fact that our ancestors were aware of this relationship between architecture and nature is the inscription on the famous well of San Patrizio which reads: quod natura munimento inviderat industria adiecit (What nature denied for defence - in this case water - was added by the work of man). Visiting this town means journeying through history, for traces of each and every period of the almost three thousand years of its existence crop up everywhere in this preconstituted physical entity.