Descriptive vocabulary (PDF - 27 Kb)
The internal structure of the building was visible from the outside : three doors opened on to three naves, the side aisles were lower than the central nave forming a second level with a large bay at the front of the building. The two levels of the facade are decorated with Lombard bands (blind arcades), showing the influence of the Lombard region on the building.
Rectangular shaped, without a transept, the cathedral is completed to the east by two apsidioles with cul-de-four vaulting and an apse destroyed in the 18th century. Strong cylindrical pillars support a steep elevation of large slightly pointed arcades, topped by tall and narrow windows.
The very original ceiling consists of a groin arch supported by a ribbed vault and squared off transverse arches.

The medieval roofing consisted of rectangular tiles, modelled on the antique tegulae.
In modern times, many changes have taken place: construction of a crypt, building of the double staircase, adding benches (pews), building of a rectangular choir area, modification of the organ tribune and building of the Saint-Sacrement Chapel, a beautiful example of Late Baroque architecture.