Thanks both for your feedback.
I had to postpone our trip to Vienna. (I found not enough information, what/where to see)
Maybe in 2 years ?
Insteat we went to the island Sylt and the island Helgoland. (Lange Anna is beautiful)
Very nice. (for those who like it)
In sylt all the German bunkers are removed.
But I'm sure that there are still some under the sand.
In the dunes from Westerland, you can see the grey concrete roof from some big ones with some antenna's in the environement.
I will try to post some pictures.