A huge abandoned military complex, once headquarters to the Nazis and then the Soviets, lies hidden inside a fenced-off pine forest in eastern Germany – but one man keeps the memories alive.

Werner Borchert grinds out a cigarette with his leather boot, zips up his jacket and unlocks a rusty door with a sign reading “Do not enter”. He’s entering anyway.

Borchert is stepping into the heart of the forbidden city in the Wuensdorf neighbourhood of Zossen, 25 miles south of Berlin.

“The Kaiser, Hitler, the Soviets – all of them were militarily active here, one after the other,” says Borchert, 67, who offers tours of the “Haus der Offiziere”, or officers’ complex.

He flicks a light switch in the darkness to turn on the cold, fluorescent lamps that light up seemingly endless hallways with numerous rooms branching off to the left and right.

Inside Germany’s abandoned ‘forbidden city’ Show all 8 1 /8 Inside Germany’s abandoned ‘forbidden city’ Inside Germany’s abandoned ‘forbidden city’ A Lenin monument stands in front of the abandoned "Haus der Offiziere" the headquarters for the Soviets' military high command in former East Germany, at the Wuensdorf neighborhood of Zossen. AP Inside Germany’s abandoned ‘forbidden city’ Photo guide Werner Borchert pose for a portrait in the main entrance of the abandoned "Haus der Offiziere", the headquarters for the Soviets' military high command in former East Germany at the Wuensdorf neighborhood of Zossen. AP Inside Germany’s abandoned ‘forbidden city’ A monument of the Soviets' stands in front of a abandoned house at the compound of the headquarters for the Soviets' military high command in former East Germany at the Wuensdorf neighborhood of Zossen Markus Schreiber AP Inside Germany’s abandoned ‘forbidden city’ The doors stand open in a corridor of the abandoned "Haus der Offiziere", the headquarters for the Soviets' military high command in Zossen, eastern Germany AP Inside Germany’s abandoned ‘forbidden city’ The staircase inside the abandoned "Haus der Offiziere", the headquarters for the Soviets' military high command in former East Germany, at the Wuensdorf neighborhood of Zossen. AP Inside Germany’s abandoned ‘forbidden city’ A Lenin monument stands in front of the abandoned "Haus der Offiziere", the headquarters for the Soviets' military high command in former East Germany, at the Wuensdorf neighborhood of Zossen. AP Inside Germany’s abandoned ‘forbidden city’ A part of the abandoned "Haus der Offiziere", the headquarters for the Soviets' military high command in former East Germany at the Wuensdorf neighborhood of Zossen. AP Inside Germany’s abandoned ‘forbidden city’ Views out of a window in the abandoned "Haus der Offiziere", the headquarters for the Soviets' military high command in former East Germany at the Wuensdorf neighborhood of Zossen AP

The complex, inaugurated in 1916, has housed the military of German Kaiser Wilhelm II, served as the Nazis’ military command centre during the Second World War – and then headquartered the Soviets’ military high command for East Germany during the Cold War.

“This was ‘Little Moscow’ on German ground,” Borchert, who grew up in the area, says during a tour. There was a theatre, a museum, shopping facilities, a swimming pool and many barracks for the 40,000 or so soldiers who were stationed here.

“It was the cultural centre for the Soviet army in Germany,” he says.

In 1994, several years after the fall of the Iron Curtain, the reunification of Germany and the disintegration of the Soviet Union, the last Russian soldiers left the compound, 2.3 square mile area enclosed by a 10.5-mile concrete wall.

The complex is now under the auspices of the state of Brandenburg, but no money has been invested and no new owner has been found. The ravages of time have taken their toll.

The faded yellow plastering is flaking off the facade, windows are broken, a fuse box dangles off a wall and wild animals such as martens have left trails of excrement on the dusty floors.

The forbidden city got its name during Soviet times because German locals were rarely allowed in. Today’s it’s mostly off-limits for the public, though tours can be booked with Borchert’s group.

Some of the vacated rooms inside the three-story officers’ complex recall the glory years of Soviet power in East Germany.

One pale mural celebrates communism, showing a hydroelectric power station and muscular workers on tractors. Outside the main-building entrance gate, there’s still an oversized statue of the Russian communist revolutionary Vladimir Lenin.

Some 20,000 visitors come to Wuensdorf every year to learn about the the town’s military history. Aside from the forbidden city, the area also still has traces of the Nazis’ Third Reich reign – including an elaborate and secretive system of bunkers.

Known as Maybach I and Maybach II, the Nazis built the fake country houses out of concrete that were supposed to disguise underground bunkers that housed the military and army high commands. This was where much of the planning of the Second World War was developed.

Most of the Maybach complex was destroyed after the end of the war by the Soviets, but the huge underground bunker known as Zeppelin, which served as a communication hub, is still accessible.

It’s also home to several above-ground air-raid bunkers known as Spitzbunker, which were rarely used but were a draw to the area for military buffs.

“This was already secretive during the Nazi times. People who lived here of course knew that it was somehow related to the military, but they didn’t know the details,” says Sylvia Rademacher, another tour guide, referring to the Zeppelin bunker.

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“Under Russian times this was just as secretive or, one could say, exterritorial – the German territory ended at the walls,” she says, adding that the Soviets, too, used the bunker for communication purposes during the Cold War.

Reflecting on what Wuensdorf’s military history means to her personally, Rademacher pauses for a moment, looking at the destroyed Maybach bunkers, and says: “For me it’s a memorial, a warning that one has to teach young people that all of this shall not happen again.”