In about 1953, as a kid visiting the area, I spent a week or two playing on the cliffs in Normandy (while my parents were involved in 'loftier matters')... Area was honeycombed with trenches which joined the German bunkers, some of which still had guns sticking out of them. I was obviously fascinated, but my parents forbade me to go into the bunkers, and I obeyed-- but spent a lot of time prowling the network of trenches.