Fortification Links:

Military Fortifications of The World
De La Fortification (French)
Vauban (The Fortress Ring)
Atlantic Wall/Atlantikwall (Dutch)
Atlantic Wall/Atlantikwall in Holland
Atlantic Wall/Atlantikwall Website
Atlantic Wall/Atlantikwall in Denmark
AtlanticWall/Atlantikwall - Association Le Mur (French)
AtlanticWall/Atlantikwall - Association Le Mur (English)
The Maginot Line/Ligne Maginot
Ouvrage aio Immerhof (French)
Fortification Immerhof (English)
Maginot Line World (English - other languages available)
The Battle of Liège 1914
Czechoslovakian fortification system
Czechoslovakian Fortesses 1935-1938
Czech Fortification K-S 5 (Czech, parts in English and German)
Suomenlinna Sveaborg - Seafortress
Cartagena Plaza Fuerte (Spanish Coast Defenses) (Spanish)
Per-Albin-line - A Swedish Maginot line? (English and Swedish)
Fortifications in Greece (Greek - other languages available)
American Coast Defenses
Fortress Bouda (Czech Fortifications) (English and Czech)
Le Comité pour la Promotion et la Sauvegarde de la Fortification (French)
Festung Norwegen - German fortifications in Norway
Vallo Alpino (Italian)
East Wall (Krawa- verlagsgemeinschaft) (German)
Der Westwall (German)
Places of World War II (English)
Le Fortificazioni del Cadore (English and Italian)
Belgian Fronts (English)
Belgian fortresses of the 20th century (Several languages)
Feste Kaiser Wilhelm II - Mutzig (Several languages)
Foundation Fort Liezele (Dutch and English)
Fortress UK
The South Coast Martello Towers (English)
Verdun (German)
Vladivostok fortress (Russian and English)
Palmerston Forts Society (Victorian Era Forts) (English)
The center for fort preservation and tourism (English)
U-Boat Bases in France during WW II (English and French)
San Francisco Defense Guns In WW II (English)
Art of Fortification
U-Boat Bases of La Rochelle-la Pallice (French and English)
Corregidor (Manila Bay) (English)
Defence Line of Amsterdam (In English)
De Stelling van Amsterdam (In Dutch)
V 2 launch site (La Coupole) (Several languages also several errors!)
Fort Eben Emael in Belgium (Several languages) - Startpage (Dutch)
Atlantic Wall - Netherlands (Dutch, English, German)
Forts of Portsmouth Harbor, New Hampshire, USA (English)
North American Fortifications Guide (English)
Stichting WOVIJ (Dutch, parts in German)