 In the case of Durham Cathedral, flying buttresses have been employed, but are hidden inside the triforium gallery.The arches used in Romanesque architecture are nearly always semicircular, for openings such as doors and windows, for vaults and for arcades.Wide doorways are usually surmounted by a semi-circular arch, except where a door with a lintel is set into a large arched recess and surmounted by a semi-circular "lunette" with decorative carving.