In addition to tons of castles in Poland, there are some left over German bunker complexes.



These are pretty big files, but you can zoom in on MG bunker and Arty bunker for a layout and the writeup (in English and Polish) if you want more of an idea of the facilities in each.

http://harbinger.twilightwar.net/mgbunker.jpeg
http://harbinger.twilightwar.net/bunker1.jpeg
http://harbinger.twilightwar.net/bunker2.jpeg
http://harbinger.twilightwar.net/bunker3.jpeg
http://harbinger.twilightwar.net/artybunker.jpeg