Neat!
When I was a boy visiting my grandparents in SW France (in the '80s) the blockhouses of the Atlantic wall were still sitting in the sand dunes... Today, for the most part, they've fallen into the sea as a result of erosion, though a few remain inland, covered in graffiti, if you know where to look for them. Of course, north of the Gironde river, where the coastline is composed of earth or rock rather than sand, the blockhouses remain. Perhaps in two thousand years they will remain, as enigmatic to our descendants as the dolmen and menhir are to us...
The amount of concrete poured by the Germans in Europe in '42-43 was absolutely phenomenal: the Wall used up over 17 million cubic metres of concrete and 1.2 million tonnes of steel.
C_G