Batterie de Cornouaille, Military fortification in Roscanvel, France.

The Batterie de Cornouaille is a coastal fortification in Roscanvel with stone walls and artillery positions that command the entrance to Brest roadstead. The site stretches along the shoreline and uses the natural elevation of the terrain to overlook the waterway.

Construction of the fortification began in 1684 under Vauban, a renowned French military engineer. It replaced an earlier plan for a nearby island that faced insurmountable challenges from strong currents and rough seas.

The name Cornouaille links the battery to the Breton region of Cornouaille; in Breton it is called Kastell Kernev. The site is now abandoned and open, and the Conservatoire du littoral has held it since the Ministry of Defence ceded it on 21 July 2009. Look for the 36 embrasures pierced along the parapet.

The site is abandoned and open, with no reception or guided tours; access on foot is via the cliff-side path, reached from the south end of the battery by a staircase. The ground lies a few metres above the water on a mined rock platform, so wear sturdy shoes and keep away from the parapet edge, which storms in late 2023 and early 2024 damaged.

In 1888 a cavity was cut beneath the cliff to house two 320 mm guns of the 1870-1884 model, firing at water level to hit the vital parts of ironclads. Two chimneys were pierced for the fumes and a stair on the north flank gave outside access. The arches supporting the escarp are cut from dressed granite, and from the sea the two firing positions are almost invisible.