The Cathedral of Sant’Andrea is located at the centre of the ancient town. The piazza surrounding it is a typical example of urban medieval planning and the town itself encompasses and expands around the building.
The church has a rectangular plan and features three naves, a trussed ceiling and lateral cross vaults, meanwhile the absis is in the shape of a semicircle. The “Ecclesia Sancti Andrea” was likely built in 1035, but construction of the building was finished years later in 1395, and in three consecutive phases: the first phase of construction occurred in the 11th century and only some architectural elements on the facade from this phase still remain today; the second phase dates back to the 12th century, when a colonnade and other medieval motifs were built alongside some classical and pre-Christian decorations; and the third phase occurred in the 14th century, when the splendid rose window and loggia was added, in Gothic style.
The interior, very suggestive, displays some artwork with a significative artistic value, such as the Annunciazione sculpture group (XIV sec.) commonly known as "Le Cassanelle”, in french Gothic style.