I have visited the Atomkeller Museum, in Haigerloch. As far as I can remember what you can see on the picture [1] from the article is almost everything there is to see. At the entrance is a glass box with a slowly ticking Geiger counter but that's it. Basically it's a small rock cavern with a hole in the ground.

[1] http://cen.acs.org/content/cen/articles/93/i39/Nuclear-Foren...