The fort du Mengant or fort du Léon in the commune of Plouzané is part of the defences of the roadstead of Brest. It is made up of a high battery, with a now-destroyed artillery tower, and a lower semi-circular battery at the foot of the cliff, with two small powder magazines.
Built by Vauban in 1684, it faces the batterie de cornouaille on the Roscanvel peninsula, built to the same model as the lower part of the fort du Mengant. The aim was to permit these two batteries, only just over 2 km apart, to bar entry to the roadstead. The original plans foresaw the completion of the defences by adding a battery in the middle of the goulet, on the Roche Mengant, but this proved impossible due to the tides and currents in the goulet.
Wikipedia https://en.wikipedia.org/wiki/Fort_du_Mengant
Address 29280, France
Coordinates 48°20'50.944" N -4°35'13.862" E