The Mont Saint Michel Abbey is located within the city and island of Mont-Saint-Michel in Lower Normandy, in the department of Manche. The abbey is an essential part of the structural composition of the town the feudal society constructed.
Suomenlinna or Sveaborg, until 1918 Viapori, is an inhabited sea fortress built on six islands and which now forms part of the city of Helsinki, the capital of Finland.
Olavinlinna is a 15th-century three-tower castle located in Savonlinna, Finland. It is the northernmost medieval stone fortress still standing.