The ancient land of the Montefeltro, lodged between the regions of Le Marche, Romagna and Tuscany, which Duke Federico (1422-1482) drew together, counted a large number of fortresses, built in medieval times to control and safeguard an impervious terrain that would otherwise have been easily conquered by enemy forces. Nonetheless, previous existent fortifications could not guarantee the strong selfdefence required by Federico da Montefeltro. This led to an ambitious project: the transformation, with the help of architects and ballistic experts, of the original fortified area into a new instrument of wartime defence, making the boundaries of the duchy impenetrable. Francesco di Giorgio Martini (1439-1501) was entrusted with this task of strengthening many of the fortresses in the area, including San Leo. The fortress of San Leo is an imposing defensive structure that seems to be an extension of the rock that supports it.
San Leo itself is a tiny hilltop village with a few houses and two beautiful Romanesque churches.