The San Leo boulder retains an invaluable heritage for the history of European military architecture and landscape. Its majesty, which impressed Dante Alighieri himself, lies in the combination of structures and natural position. Precarious position which, over the centuries, has resulted in the loss by landslide of many of its original volumes. The boulder is so far back that the Fortress stands on tiptoe on the edge of the precipice in a continuous race against time for its conservation. Through the disciplines ofArcheologia dell’architettura and of Architectural Restoration this volume launches a new course for the Fortress, constituting a useful reading, understanding and protection tool for professionals and for all those who find ideas of keen interest in the issues of conservation and use of the Cultural Property.