Just about all the other blogs that deal with Lost Places of Berlin will list Wünsdorf, or Lenin's Forbidden City as it is also called. Technically, however, this place no longer belongs to Berlin but Teltow-Flemming, Brandenburg. It is an hour's drive by car from Berlin proper, or a slightly longer ride if you take the train.
I was mentally prepared to explore the area surrounding the former Officers' Quarters occupied by the Soviet Union Army during the Cold War, and previously by the German Army during WWII, however, once we got there, we were greeted by barricades and fences. Like many other Lost Places in Berlin, it has been taken over by a construction conglomerate and is not part of a major gentrification project of Wünsdorf and Waldstadt. Adventurous though one might be and I could have squeezed through the fences, there are CCTV cameras all over the place, and Germany is not the country to violate a No Entry sign.
The Officers' House may be a main attraction, but it is not the alpha and omega of the exploration. Continue past the main House and you will encounter the former army mechanical station. Though it is also behind a fence, parts of it can still be photographed, leaving me to wonder what it all must have looked like during the best of times.
The entire area requires a bike or a car to explore. You definitely can't do it on food because various stations and bunkers are scattered around. Zossen, Wünsdorf and Waldstadt host massive underground and above ground bunkers (Spitzbunker). The first of them is called Zeppelin, built between 1937-1939 as the signal Intelligence Centre. Maybach I and II were completed in 1939 and 1949 respectively, consisting of above-ground houses that were deceivingly normal in appearance but to a complex subterranean maze fortified by thick walls and fully equipped with water and ventilation systems.
Much of the infrastructure was destroyed by the Soviet Forces in 1946, after which they took over the compound. The Zeppelin compound was absorbed into the Soviet Intelligence Center during Cold War and was renamed as Ranet. To get a closer look inside the bunkers you need to book a guided tour and be prepared to spend several hours in the area.
There is hardly anything that you can access independently. Nevertheless, it was worth the trip anyway, just to see the peculiar Spitzbunker structures. By the time we left, the weather was taking a turn for the worse, giving the entire complex a very eerie feeling.