The Fortress of San Leo located at the highest point of a rocky plate bordered by imposing vertical walls, the fortress represents the main architectural emergency of the entire village of San Leo. The origins of the fortified town are certainly pre-Christian, although the first documented news of a real settlement are linked to the presence of the holy Lion between the fourth and fifth centuries. The remarkable strategic position made San Leo a disputed place throughout the early Middle Ages: from the Goths to the Byzantines, passing through the Lombards (Desiderio built the first defensive garrison in masonry) up to the domination of the Church, attested from the mid-eighth until most of the tenth century.

La Pieve is the oldest religious monument of San Leo and the entire territory of Montefeltro. It is the first material testimony of the Christianization of this area of the hinterland: the primitive cell of a history that mixes and confuses with tradition.

It is certainly the highest example of medieval architecture preserved in Montefeltro and is one of the most unique and important testimonies of Romanesque-Lombard architecture. The church preserves an exceptional sculptural kit that includes, in addition to the Corinthian capitals of the third century (d.C.), numerous Romanesque capitals variously figured, the oldest of which represent the symbols of early Christianity.