A ramshackle, two-storey wooden structure on a traffic island in Berlin’s Kreuzberg district has become the centre of a preservation battle. Supporters of the Treehouse at the Wall, built by Turkish guest worker Osman Kalin on a former no man’s land beside the Berlin Wall, fear it may be demolished by the city as a public safety hazard.
In 1983, Kalin, a Turkish “guest worker”, was looking for a patch of earth in his corner of the city cleaved by the Berlin Wall to plant onions, garlic and cucumbers. Near his home, the east-west border cut a sharp angle by the curved street Bethaniendamm, leaving a triangular scrap of no man’s land next to the concrete wall and barbed wire. Although it sat in West Berlin, the lot officially belonged to communist East Germany, so neither side used it and it became a dump for orphaned furniture and discarded drug paraphernalia.
Kalin saw potential in the postage stamp of fertile soil beneath that debris. He at first squatted the land with a flower and vegetable garden and a small improvised shed. He later won permission from East German authorities to stay, on condition that whatever he built there would not be taller than the wall. In time he replaced the shed with the larger treehouse, which despite its name is not up in the branches but built around a mature trunk on the site.
A guerrilla garden in a divided city
Over the decades, the “guerrilla garden” came to symbolise a rebel spirit in dark times, the ingenuity of immigrants who were often made to feel unwelcome, and the tragedy and absurdity of great-power confrontation in a city where people on both sides wanted to breathe free. Four decades of upheaval have left their mark, and now supporters fear the structure could be torn down as a safety hazard.
Kalin was born in Anatolia in 1925 and arrived in West Germany in the late 1960s as a manual labourer. Under the guest worker programme, about 14 million people came to the country between 1955 and 1973. Many stayed; nearly 3 million people of Turkish origin now live in Germany, about 200,000 of them in Berlin.
After the city reunited in 1990, Kalin faced eviction orders but found an unlikely ally in the neighbouring St Thomas church, which located 18th-century papers showing it was the rightful owner of the land and allowed him to stay. Since Kalin’s death in 2018, his son Mehmet has tended the property and his father’s legacy.
A symbol of resistance and a memorial
Suat Özkan, general secretary of a Turkish community group in Berlin, described Kalin as “a remarkable figure”. He said: “Perhaps he wasn’t a master of language, perhaps he wasn’t the perfect architect, perhaps he wasn’t the perfect artist, but he created something artistic – something that became totally unique.”
Özkan also said Kalin’s act was one of political defiance. “Right when two global political systems were facing off,” he said, Osman Kalin carried out an “act of defiance against the GDR regime, against the system, to show that it is possible to stand up and carry out a kind of revolution”. He added: “It’s a symbol of resistance as well as a symbol against racism, discrimination and hostility.”
More than six decades after West Germany established the guest worker programme, Özkan said it was long past time for the united country to pay tribute to its waves of immigrants. “We still haven’t managed to construct a central memorial,” he said. “This house should serve as a kind of memorial.”
A long-delayed tribute
Stefan Zeppenfeld, a historian who published a book in 2021 about Turkish labourers in West Berlin during the cold war, said Germany had taken decades to acknowledge its transformation into a “country of immigration”. He noted that migrant labourers like Kalin were relegated to neighbourhoods close to the wall, such as Kreuzberg, which became prime real estate after the wall’s fall in 1989.
Zeppenfeld said the treehouse crystallised many aspects of what made up Berlin and its people. “The history of German division or the iron curtain is still absolutely crucial and defining for Berlin, for Berlin’s sense of identity,” he said. “And I find it absolutely fascinating that this building is still standing – it’s one of the few tangible legacies where we can actually see agency by Turkish guest workers as a real part of the cityscape.”
As a first step, Özkan is planning an open-air exhibition on the chain-link fence surrounding the structure, complete with archival pictures and Kalin’s extraordinary life story. The tension with city authorities ahead of a Berlin election in September is that supporters want to maintain the treehouse’s scruffy authenticity, while safety and legal concerns have forced a conversation about its structural integrity.
Efforts to save the treehouse
Outside, the wooden facade is made up of listing, mismatched planks. Tongue-in-cheek Nato and Soviet flags whip from erected poles while plum and apple trees mark the seasons. Inside, a jumble of black-and-white photographs and construction tools point to the Kalin family’s past and future in their garden idyll, with a donated chandelier lending an unexpected touch of elegance.
Florian Schmidt, a Kreuzberg district councillor, said his office was working closely with the Turkish community and Kalin’s son Mehmet, who has done extensive repairs on the house, to “grant the necessary permits” for it to remain. “Due to the unusual situation – the site being a no man’s land and the lack of planning permission – use of the treehouse was initially prohibited,” Schmidt said, noting that Mehmet had been granted a temporary exemption to do work there. “Issues relating to ownership rights are also being clarified.”
Adrian Sampson, of Alternative Berlin Tours, which spotlights the city’s subculture and street art, was leading a group of visitors past the treehouse on a hot July day as he explained Kalin’s legacy. “His story is about three things: resistance, community spirit and multiculture all together there. And that’s what Kreuzberg is about,” he said. Asked about speculation that the site’s days could be numbered, he said: “I think it’d be an absolute shame, like really a pity for the city, because it just makes a lot of people happy.”
