Romanesque builders have created a totally-vaulted basilica with groin vaults in the aisles and groin or barrel vaults in the main vessel. Since the heavy masonry of the vaulting creates considerable outward thrust it has been necessary to thicken the main supports (no longer columns but compound piers) and outer walls which are stiffened by shallow buttresses. Windows are small. The interior is now dark and optical continuity is obstructed by the substantial supports. An example of such a structure with a barrel vault is Saint-Etienne in Nevers.