I suppose most people seeing this will be divided into two camps. One will wonder why in the the world anyone would be interested in traipsing around inside old building. The other knows exactly why it's so fascinating. If you are in that second camp I would strongly suggest you visit my Picasaweb page, press F11 to go to full-screen mode and click the slideshow icon.
If you google "Beelitz" or "Beelitz-Heilstätten" you will get many hit's and find a lot more information.
If you are really in the second camp you can also check out a documentary on the subject.
There is a full hour and a half documentary on You Tube. I think it may disappear from there but try and see if it's still availible.