Aosta Cathedral is a Roman Catholic cathedral in Aosta, in north-west Italy, built in the 4th century. It is the episcopal seat of the Diocese of Aosta. In the 11th century the Palaeo-Christian structure was replaced by a new one, dedicated to the Assumption of the Virgin Mary and Saint John the Baptist. The architecture of the cathedral was modified during the 15th and 16th century. The present façade, in Neoclassical style, was built between 1846 and 1848. It surrounds the 16th century portal in Renaissance style, decorated with statues and frescoes showing scenes of the life of the Virgin Mary. The structures remaining from the Romanesque period are two clock-towers and the crypt, and also the remaining part of an Ottonian fresco cycle on the church ceiling.