I took advantage of a week's holiday in Brittany to explore several centuries' worth of fortifications and museums. (See also my previous military museum raid on Brittany to St Cyr.) Most of this reconnaissance was done during day's tour of the Crozon peninsula along the Route des Fortifications. The Crozon tourism office provides a nice downloadable brochure here.
Captioned photos below give the details. In summary:
Wars of Religion: Pointe des Espagnols
C17: Tour Vauban
French Revolution/Napoleonics: coastal batteries and garrison towers; Musée Vendée Chouannerie; Phare d'Eckmühl
C19: Fort Kador; coastal batteries
WWI: 32cm gun
WWII: lots of coastal bunkers; Battle of the Atlantic museum; Lorient submarine pens.
(The photos are grouped by site rather than in any special chronological or geographical order, so if you're interested in one conflict or site in particular, sorry but you'll just have to search/scroll.)
Morgat is the small port of Crozon on the south coast of the peninsula. In the mid-C19 a system of fortifications was built to defend it, including the upper and lower Kador batteries.