We have grouped together, under his terms, the means of defence which organize the defence of a territory. They are a means of observation such as the Genoese towers of Corsica. Some Donjon, are the only remains of the castle. As for the citadelles and bastions, they were born primarily under Louis XIV. It was about defending our borders, "the pre-square" Vauban wanted.
For clarity we have separated them into 3 sub-categories:
Donjons Tours Citadels
NB: For regions that have not been regrouped, namely: Bretagne, Centre-Val-de-Loire, Corse, Île-de-France, Pays-de-la-Loire, Provence-Alpes-Côte-D'azur, you must not go through the navigation opposite, but by the "classic" route below, to discover the subcategories of your department.