Marcel Krueger takes a ride on the U6 to explore Berlin’s GDR-era “ghost stations.”

I’VE BEEN fascinated by the subway all my life. Maybe it’s the fact that there’s nothing outside the windows, that when sitting in a subway carriage one has no other choice than to focus on the other passengers — how they look, what they’re doing, what they’re reading — or, god forbid, oneself.

There’s also that unique feeling of descending into the bowels of a city and being propelled from one brightly lit station to the next through dark, mysterious tunnels.

In Berlin, there is the additional sensation of stepping out of the present and directly into subterranean history, since the city’s U-Bahn and S-Bahn were both engaged in transporting border traffic between West Germany and the GDR.

The fact that the city was divided along apparently randomly drawn borders meant some of the U-Bahn lines from West Berlin actually traveled beneath East Berlin, though passengers were not able to leave the train until it reached West Berlin again. The stations those trains passed soon became known as “ghost stations” amongst Berliners — dimly lit stops where armed East German border guards would peer at passengers through slits in bricked-up huts.

See portraits of the entire U6 line in photographer Kate Seabrook’s photo essay.

Due to the geography of the boroughs of Wedding in the West and Mitte in the East, the U6 had, after the U8, the second highest number of ghost stations, namely the five stations from Schwartzkopffstraße to Stadtmitte. On a cold March day in a still snow-covered Berlin, I decided to ride the U6 to Friedrichstrasse. I wanted to get a feel for what the underground city may have looked and felt like during those Cold War days, and to simulate a journey from West to East, if only in my head.

* * *

I start right at the beginning of the U6, at Alt-Tegel, which opened as Tegel station in 1958 as part of a northern extension of the U6, which had existed since 1923 as the north-south line between Seestrasse and Tempelhof. In 1992, the station was renamed Alt-Tegel (Old Tegel). As it’s the end of the line, it comprises eight exits, and is an important feeder in summer for people visiting the nearby Tegeler See to explore its pleasure boats and beaches.

On this cold, winter day, though, the area reminds me of the small, boring town in West Germany I grew up in: all 1980s plastic and concrete with sharp edges, a Commerzbank, and a C&A next to a café full of huddled, grey-haired pensioners.

GDR U-Bahn and S-Bahn. West Berlin does not exist on this map.

Borsigwerke, Holzhauser Straße, Otisstraße, and Scharnweberstraße are the next stops on the line, also part of the 1958 extension.

Due to the very high water table, the track was raised onto an embankment, meaning passengers can view the quintessential urban scenery: business parks, small estates, grey and brown houses from the ’80s.

The only excitement for me is at Scharnweberstrasse, where one can see glimpses of the planes rolling along the runway of Tegel Airport.

Speaking of planes: Kurt-Schumacher-Platz must be the best place in Berlin for plane spotting. There’s something genuinely appealing about standing at the bus stop near the kebab stands and Chinese restaurants and watching the planes roar just 50 metres overhead on their final approach to Tegel.

The locals, long used to the noise and the sight of planes with landing gear extended, continue strolling and feeding the pigeons without blinking. For visitors like me, it’s hard not to imagine the plane careening into the bus stop rather than the runway behind it.

From Kurt-Schumacher-Platz, the U-Bahn runs underground again, traveling through “wild” Wedding (formerly in the French occupation sector) along Afrikanische Straße (with the nearby Centre Culturel Français and its very own Eiffel Tower replica), Rehberge (the best stop to explore the Siedlung Schillerpark, a modernist housing estate and UNESCO World Heritage Site), Seestraße, and Leopoldplatz — aka the heart of Wedding, with its Brutalist town hall and Schinkel-designed church — and to Reinickendorfer Straße, the former “last stop in Berlin West.”

From 1961 on, when the wall was erected, trains from Reinickendorfer Straße did not stop until Friedrichstrasse. The line was then called the C-line, and its trains would pass under the border and through Schwartzkopffstraße (then Stadion der Weltjugend), Naturkundenmuseum (then Nordbahnhof), and Oranienburger Tor at a snail’s pace.

All the station exits were bricked up, and armed border guards or police patrolled the platforms vigilantly. There was barbed wire beneath the platform edge to prevent fugitives from crawling along the tracks, and even the emergency exists were blocked — the only way to leave when a train broke down was to walk along the tracks to the nearest Western station.

On the surface, all references to these stations were removed; the GDR did not want to remind its citizens that there were trains rumbling in and out of the capitalist West right beneath their feet. Today, nothing reminds passengers that these stations, now cheerfully painted in yellows and greens, had once been in another country — except maybe a vaguely claustrophobic atmosphere.

Although there are no tangible traces of the U6’s ghost stations, there is a free exhibition on the subject at Nordbahnhof S-Bahn station (entrance on Gartenstrasse, on the mezzanine), which is open during the station’s hours of operation.

The stations seem smaller and more crowded than the ones further up the line, but that could admittedly be my imagination. The atmosphere doesn’t seem to affect the school classes alighting at Naturkundemuseum, nor the noisy group of Spanish tourists entering the carriage at Oranienburger Tor for the short hop to Friedrichstrasse.

Bahnhof Friedrichstrasse is one of the most important stations in Berlin history. Different to the other GDR ghost stations, it was transformed from a former central station for subway, commuter, and regional trains into a major border crossing, and became a bottleneck where people from the capitalist West and from the workers’ and peasants’ state passed each other unseen.

The station’s facilities and the underground station were only accessible for passengers from the Western sectors transferring here. West Berlin citizens could also avail of the border crossing and enter the GDR here, after passing through a labyrinthine maze of tunnels and walkways designed to prevent any direct contact with GDR citizens.

East Berliners, on the other hand, could not enter the U- or S-Bahn — the only way to leave the GDR was to get on a long-distance train to West Germany. To do so, GDR citizens had to pass through the so-called Tränenpalast, the palace of tears, a building on the square north of the station erected in 1962. The expression is derived from the tearful goodbyes that took place in front of the building, where family members with travel permits had to say farewell to their relatives.

After the fall of the wall, the blue glass pavilion of Friedrichstrasse became a cultural center for concerts and readings, and was eventually turned into the Tränenpalast museum in 2006, enabling visitors to relive the experience of officially crossing from the GDR to West Berlin.

This story was written by Marcel Krueger and originally appeared at Slow Travel Berlin, who publish in-depth dispatches from the city, run intimate tours and creative workshops, and have produced their own companion guide full of insider tips.