Wünsdorf was known as a forbidden city, because right here a soviet military base that located. It was used by USSR, later Russia until 1994. Today Wunsdorf is an open civil city, with a few museums that are telling about it's past. One of these museums is Bunkerstadt Wünsdorf, it provides guided tours in German inside the bunker.
At specific dates you have an opportunity to visit a bunker with a special route which shows more than a standard tour.