Complex Sant Orso, dedicated to the saint Ursu Aostskomu - this is one of the major attractions of the city of Aosta and one of the most interesting religious complexes in the Alps consisting of the churches of St. Peter and St. Orso, freestanding wonderful bell tower, superb cloister and a small monastery in the Renaissance style.

In ancient times on the site of the complex Sant Orso has a vast necropolis of the city, on whose territory in the 5th century, it was built the early Christian church. The original building of the church of San Orso consisted of one room, a limited semicircular apse. In the 9th century, during the reign of the Carolingian dynasty, it has been completely rebuilt. Later, on the initiative of the local bishop Anselm in the church, it was another reconstruction - this time it was built according to the plan of the basilica with three naves with wooden trusses. The last in the 15th century replaced the Gothic Groin vault. For the same period include Gothic choir and mosaics.

Today in the church of Sant Orso kept many Missal - the liturgical books and reliquaries, including the relics of St. Ursus, which rest in the crypt, and the relics of St. Gratusa Aostiyskogo. Of particular note is the church cloister decorated with figures of people and animals capitals, which depict scenes from the life of Ursa Aostiyskogo - it is called "marble masterpiece". Cloister consists of 37 marble columns, although its northern part in the 18th century was demolished.

44-meter high bell tower of the complex, built in the year 989, has retained some of the original medieval structure, although its present Romanesque appearance it acquired in the 12th century. Inside the church, in the space between the current and original vault ceiling, fragments of Romanesque murals depicting scenes from the New Testament.