One of the 15.000 nazi bunkers along the Atlantic coast; this one at Cap Blanc Nez, Northern France where I just spent a couple of days.
The best collection of photographs of the Atlantic Wall is by Paul Virilio:
Bunker Archeology: Texts and Photos (1975) – Paul Virilio [Amazon US] [FR] [DE] [UK]
I have saw a photo show last year about this bunker. I have to said that they were a really good photos. Amazing.