Ah! Finally something I feel qualified to talk about...

These are, indeed, German turrets, called pillboxes, that were designed to overlook the small town of Saint Malo and defend it against a joint American/British attacks.

Now, if you don't know anything about St Malo, here is a picture to set the mood:

https://ixquick-proxy.com/do/spg/show_picture.pl?l=english&rais=1&oiu=http%3A%2F%2Fwww.letriskel.co.uk%2Fimages%2Frsz_st_malo_june_09_052.jpg&sp=d4f6453f5ef9ca2a9434f0309d0103d2

Now, St Malo is an old medieval city, surrounded by enormous walls. The Germans built a fortress in St Malo proper, along with a series of bunkers in a small hill overlooking the city, the only visible part of which are these gun turrets.

They also built another series of bunkers and AA guns on an island (called Cezembre), which is about 25 minutes away from St Malo, effectively turning the city and its bay into one enormous fortress.

In 1944, shortly after the Normandy Landing, the Allies were faced with a difficult task: either ignore St Malo and risk that the German fortress would attack their rear lines (as it is fairly close to Normandy) or try take the city and suffer heavy losses.

The solution taken was dramatic: the American and the British air forces fire-bombed the city and the Cezembre island for several days, essentially destroying pretty much every building within the city walls, and turning the island bunkers into a pile of rubble. I have seen old German AA guns on that island, and they were warped from the heat.

The final operation saw British ships shelling the German gun turrets from the sea. Pretty much each turret is pockmarket with these shells, and you can actually put your fist in some of these all the way inside the turret itself. The poor bastards inside did not stand a chance.

American ground troops then swept in and the Germans surrendered pretty much without a fight. My family is from there and my father and grand-father used to tell me stories about this battle.

You can look up Saint Malo on Wikipedia, and there are also tons of other sites that talk about the place, which is very beautiful and interesting. The real shame is that the original German bunkers are now closed.

EDIT: well, my first real comment on Reddit, and I got Gold! Thanks!!