Here http://landships.free.fr/forum/viewtopic.php?p=1260#1260 some photos of the Kaiser Willhem II Fortress. The strongest (and modern) fort of WWI built to prevent an attack of french armies against Strasbourg and the (german) Alsace Plain.
Comments are in french but enjoy the pictures.
For more informations http://www.fort-mutzig.eu/index_gbus.html (english spoken )
Come and see!