top of page
  • Writer's pictureMatti Geyer

How an illegally built treehouse became one of Berlin's most unusual sights

Updated: 2 days ago

In the heart of Berlin, where the districts of Mitte and Kreuzberg converge, there lies a peculiar structure that has become more than just a house—it's a symbol of resilience, defiance, and a testament to the unyielding spirit of its creator, Osman Kalin. Fondly known as the "Baumhaus" or Treehouse, this two-story construction stands as a living memory of a divided city and the remarkable journey of a Turkish immigrant.

A Garden Born from Division

Osman Kalin, a Turkish immigrant who moved to Berlin in 1980, found himself living in Kreuzberg, just beside a peculiar plot of land. This triangular piece, a relic of the divided city, belonged to East Berlin but found itself on the western side of the Wall. This meant that West Berlin had no authority over the land, and the East didn't care about it. Osman, a retiree and father of six, saw potential where others saw neglect.

In the early '80s, he embarked on a mission to transform the unused land into a vegetable garden. Undeterred by the complexities of the Berlin Wall, Kalin's resilience overcame bureaucratic challenges and initial skepticism from both East and West Berlin authorities. His project, born from a desire to reconnect with his rural roots, soon grew into something extraordinary.

The Birth of the Treehouse

Facing restrictions on the height of his structures due to concerns of tunneling, Kalin initially built a single-story cabin. Eventually East Germany allowed him the usage of the land, also because they realised that this would annoy Western authorities. Kalin's daily interactions with the guards, including sharing onions and Christmas cards, reflected an unlikely camaraderie in the midst of Cold War tensions. After the Fall of the Berlin Wall, he expanded his garden and constructed a two-story treehouse around a central tree. The "Baumhaus" had electricity, running water, a bedroom, and a study—an unconventional dwelling that defied the norms. The Treehouse on the Wall became a symbol of resistance and an embodiment of the spirit of Kreuzberg.

Challenges and Triumphs

Osman Kalin faced numerous challenges, from resisting eviction attempts to dealing with the consequences of unauthorized water usage. His bold stand against authorities, coupled with the support of the local community, especially the St. Thomas Church, eventually led to the official re-drawing of the border. The garden, once in the Eastern district of Mitte, was now firmly in West Berlin's Kreuzberg—a victory for the people and for Kalin's vision.

Legacy and Future

Osman Kalin's legacy lives on. Though he passed away in 2018, his family continues to maintain the garden. Plans to turn the Baumhaus into a museum or an official monument are underway, ensuring that this symbol of unity and defiance endures.

Rediscovering Berlin's Treehouse on the Wall

If you seek Berlin's Treehouse on the Wall, head to Bethaniendamm Passage 0, near the Spree, at the intersection of Mitte and Kreuzberg. This imaginative address for a real place has become a testament to the city's reunification since the fall of the Wall. You may also join me on either a Kreuzberg, a Berlin Wall or an extended "Off the Beaten Path tour" to get here.


The Baumhaus an der Mauer stands not just as a physical structure but as a living narrative of a man's determination to cultivate life in the midst of division. Osman Kalin's Treehouse on the Wall transcends its physical boundaries, becoming a living testament to the resilience of the human spirit against the backdrop of Berlin's tumultuous history.

11 views0 comments


bottom of page