German fortifications of World War II

Bunkersite: A lot of extensive information about the Atlantic Wall, including details and plans of the bunkers and a guide to decoration, stencils and camouflage of the bunkers
H O W I T Z E R . D K: Excellent reference guide, with photographs of several battlefields of Western Europe, as well as many AFVs. Also includes an extensive model gallery
lostplaces.de: Very interesting website, shoing both historical and present-day photographs of German World War II bunkers and buildings, along with thorough descriptions of the complexes
The Atlantikwall Website: A lot of interesting information about the Atlantic Wall
Tunnel and Shelter researching: Articles and photographs of German underground bunkers
wk2relikte.de: Excellent photographic documentation of the West Wall and the Maginot Line, with many both interior and exterior photographs