Behind two-meter thick concrete walls designed to withstand an air raid attack, resides a surprising array of sights, sounds, and smells. Shut off from natural light and outside noise, the selected artworks of the Boros Collection are disturbed only by small guided tours. Berlin boasts an abundance of unique converted cultural spaces; contemporary art can be found in former train stations, churches, power stations, a brewery, a Jewish girls’ school, a crematorium, and here in a Nazi war bunker. This bunker tells a history tied closely to the modern history of the city itself. From World War II and a divided country to reunification and a mecca for counter culture nightlife, it now reflects the thriving international contemporary art capital as the exhibition space of art collector duo Christian and Karen Boros.

Built in 1942 by forced labour and under the supervision of Albert Speer, the five-story bunker could shelter 3,000 people. Seized by Russia’s Red Army, the bunker then detained prisoners of war. In the subsequent GDR years, the concrete monolith’s purpose became storage, first for textiles then tropical fruit due to its constant temperature, prompting the nickname banana bunker. After reunification and through the early nineties, the bunker became a site for Berlin’s exploding techno and fetish scene. The wild illegal raves earned the bunker the reputation as the hardest club in the world until authorities shut it down in 1995. Changing from state to private hands, but remaining a space for cultural endeavours, the bunker was finally bought by its current owners in 2003. By 2008 the interior reconstruction was complete and the first presentation of the Boros Collection opened its heavy reinforced doors to the public.

The eccentric and exclusive art experience of the Boros bunker proved a huge success. The Boroses extended the first exhibition after a flood of requests from the public who wanted to catch a glimpse inside the mysterious walls. Now, the four-year presentation format is in its third chapter, with over 200,000 guests in more than 9000 tours visiting the Boros Collection/Bunker #2 exhibition that ran between 2012 and 2016. Each new presentation reshapes the bunker’s 3000-square-meter interior as spaces are redefined to house the next set of artworks. The original 120 low-ceilinged rooms have given way to 80 gallery spaces of different proportions, some three stories high like the space carved out to fit Olafur Eliasson’s swinging suspended electric fan installation Ventilator (1997) from Boros Collection / Bunker #1.

The Boroses do not shy away from works that pose a spatial challenge. Balconies were removed to install Ai Weiwei’s Tree (2010), which fills a two-storey gallery with only a few centimeters to spare. Christian and Karen Boros have also invited some artists to create site specific works, such as duo Manon Awst and Benjamin Walther whose Latent Measures (2011) installation has pipes going from room to room, seemingly penetrating the solid concrete walls, and Line of Fire (2012) appears as if a bronze arrow was shot precisely through a tiny hole in the thick exterior wall. In these specially adapted gallery spaces that each house only one artist or work, the viewing experience is intimate and sometimes confronting. Like Eliasson’s Ventilator, some artworks impose on the viewer and demand space. Michael Sailstorfer’s Forst (2010) occupied a room with a huge tree branch endlessly rotating and scraping the ground. A large but silent repurposed church bell, For Whom… (2008) by Kris Martin, swung above visitors’ heads as they checked into their Bunker #1 tours.

Spatial dynamics have also been shaped and challenged by sensory assertions by the collection’s artists. Alicja Kwade’s Der Tag Ohne Gestern (2009) amplified a constant drone from fluorescent lights, bouncing sound between curved panels of varnished black steel. Another bell, this time installed by Thomas Zipp and attached to a rope for visitors to yank, created sporadic deafening chimes throughout the building. Sailstorfer assaulted nostrils with burning rubber from a skidding tyre and whetted appetites with a popcorn machine, which over four years filled the gallery room with popcorn and filled the neighbouring galleries with that familiar cinema lobby smell. Johannes Wohnseifer’s Black Tape (2017) in the current Bunker #3 gives guests free reign with a roll of duct tape, evoking the graffitied walls of the bunker’s club days.

In the bunker’s up-close and confined environment visitors are forced to engage with the works in one way or another. As part of a tour with an open and enthusiastic guide, viewers are given context and insights into the works, but also encouraged to share what comes to mind. The collection’s tour-only public access may seem pretentious and restrictive to some, but the fire department only allows 12 visitors at once—that’s the price for exhibiting in such a space. The upside of these restrictions is an art experience more immersive, committed, and personal than the typical museum visit. In an interview with journalist Silke Hohmann, Christian Boros described touring the bunker as intense and exhausting, “it’s an encounter with the self, and perhaps even a type of torture. The tour is a kind of pilgrimage.”

For the Boros family, the collection and its visitors are inseparable from everyday life. They live on the top floor of the bunker in a 450-square-meter glass penthouse with views over Berlin’s Mitte district. The sounds and smells of the works travel upstairs and the coming and going of visitors is felt. “We’re never alone,” Karen Boros told Hohmann, “we not only live with art, we also live with the guests.” Christian Boros still enjoys leading tours himself. The 700-piece collection is a growing and changing personal journey for the couple. Christian, the founder of a German advertising agency, has been collecting since he was 18 years old. In the early 1990s, he bought up Wolfgang Tillmanns works, intuiting the photographer’s rise to popularity. Tillmanns himself had attended and photographed the bunker’s club parties. His works from this era, presented in Bunker #2, still feel fresh and boundary pushing.

During reconstruction, the Boroses made the choice to leave traces of the bunker’s history. Some gallery walls bear graffiti and others the black paint of the club’s dark rooms. In excavated galleries you can see a horizontal line denoting the low ceilings of the crammed bomb shelter rooms, and later the sweaty packed club rooms. This choice can be at odds with the building’s new purpose—the rough, unrenovated concrete walls present a challenge to artists installing their works. The bunker is as much a site of cultural heritage—both good and bad—as it is a contemporary art gallery. The forward-looking art collection saves the building from simply being a mausoleum for the past; it is a living part of the city’s dynamic cultural landscape.