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On a sunny July day in 1957, crowds of politicians and citizens from West Berlin gathered around the Hansaplatz, an area next to the city’s historic Tiergarten park. They had convened for the debut of the City of Tomorrow, an ambitious urban planning project to restore the extensively war-damaged, 60-acre neighbourhood. More than 50 renowned architects from 14 different countries had been asked to design edifices that were to present new forms of living; by the summer of 1957 about 30 buildings had been erected. Completed by the early 1960s, the quarter remains a midcentury architectural showcase: among the most notable buildings are an eight-storey building designed by Alvar Aalto, a seven-storey Oscar Niemeyer apartment block, a “vertical city” with 527 apartments designed by Le Corbusier, bungalows conceived by Danish architect Arne Jacobsen, and German architect Ludwig Lemmer’s memorial church.

The Eternithaus, built in 1957 by Paul Baumgarten, viewed from the back © Robert Rieger

But one of the most interesting and compelling solutions for future living in the neighbourhood was the Eternithaus, designed by Berlin-based Paul Baumgarten. Instead of creating seven terraced houses, he imagined and built what he called a “residential ship” with seven 1,000sq ft two-storey maisonettes topped with private rooftop terraces. The ground floor, designed to be a commercial space, was almost completely encased in glass, creating the illusion of a floating floor above the park.

Initially the lower floor was used as a showroom for Eternit, a company manufacturing cement-building materials; the building was named after the brand as it had sponsored its cost and its bright red cursive font signage remains on the façade. In the ’80s, Eternit sold the building, and for the following two decades it was partially used as offices. By the mid-2000s however, it was empty. Entrepreneur David Fuld would pass by on his commute every morning and imagine how fantastic it would be to base his hospitality company, Fuldwerk, there. In 2007, he seized the chance to rent it. “Once I entered the ground floor I was immediately taken by the space – the light, the openness,” he says. “But it was in awful shape.”

A vintage lounge chair, found at Felix Bachmann Antiques, Berlin, in the Glass Block Room. The ’60s sideboard is from Morentz in the Netherlands © Robert Rieger

The building arcade and original Eternithaus signage from the 1960s © Robert Rieger

David Fuld and Sarah-Joan Fuld; the floorlamp is by Beltrami & Gencarelli © Robert Rieger

Lola Light by Gonzalez Haase AAS, produced by Analog Glass © Robert Rieger

David set up his offices on one side of the building, added a bar in the middle, fixed up the garden and restored the Glass Block Room – an 860sq ft space that he uses for meetings and workshops. Every time one of the flats above would come up for rent, he would attempt to buy or lease it. “I actually used the first apartment as a guest room,” he says of his first acquisition. “In the beginning I wanted to take them over because sometimes the tenants would complain when we were working late or hanging out at the bar.” Over the course of the past 15 years, he has managed to get his hands on three flats, two of which he uses personally. “I moved into one in 2021 after my divorce and I use a second apartment for guests and my adult sons,” he adds.

Over Christmas in 2022, David’s sister Sarah-Joan Fuld, a design consultant who owns a Munich-based agency, came to visit. The 54-year-old has spent several decades conceiving creative work environments, including The Fuld, a mixed-use event and office space in a townhouse in Munich; she is also the editor of a recently published book about workplace design, Where Future Grows (Niggli, €49.90).

Gonzalez Haase AAS’s objects on display in the Glass Block Room for Berlin Art Week’s Architecture Art Objects Colours, September 2025 © Robert Rieger

Vintage Arne Vodder extendable dining table, in the Glass Block Room © Robert Rieger

A kitchen in one of the apartments on the second floor of the building © Robert Rieger

“I came over at Christmas and told David that he just did not have the right furniture in the apartment,” she says. “We then spent three fun days buying things – vintage rugs, original Eero Saarinen tables and Jean Prouvé chairs – at really special design resources in Berlin like Wildcarpets, the antique dealer Felix Bachmann and Firma London.” Later, she moved her attention to the Glass Block Room. “It had horrible furniture that hurt my eyes,” she says. “I said to David, ‘Can we change it, please?’” Together they wandered through the vast warehouses of Morentz in the Netherlands, before extending the search to Sweden and Studio Schalling, where they picked up a 21ft rosewood table. “Restoring this building inspired a great passion for art and design,” David says.

A light-filled living room in one of the apartments © Robert Rieger

By this point David’s mission had changed. “It’s such a special building; it was important not only to preserve it but open it up occasionally for others to enjoy,” he says. The Glass Block Room is available for bookings by private companies, and the apartment for events and shoots. A visit with his sister to The Rope, a gallery for collectable design in Munich, at the start of this year sparked an art project and exhibition. Then this summer, the siblings approached Judith Haase of the experimental Berlin-based architecture studio Gonzalez Haase, asking if she would like to create an intervention during Berlin’s annual Art Week; she immediately said yes. “The first field trip I took as an architecture student in Berlin was to the Hansaviertel,” says Haase. “We all stood in front of the Eternithaus and couldn’t get in. No one opened the door because it was private.” Berlin, she adds, “is pioneering because it’s a place where every space has been converted into an exhibition space. Presenting art in a glass cube – essentially a room without walls – is yet another example of how you can use architecture to create a dynamic context for art.”

Hundreds of people came to the exhibitions – as much to experience the Eternithaus as to take in the art. It is the beginning of a new chapter for the building. “Once or twice a year we want to open the doors and do something that surprises us,” says David. “We don’t want to make money – we want to have fun.” Next year the pair plan to invite artists or galleries from outside Germany to engage with Eternithaus. “We want to bring an international crowd here too,” says Sarah-Joan. “This building, the neighbourhood and its architecture are all important archetypes, not just for Berlin but for other cities.” More than a generation after it was conceived as part of the City of Tomorrow, the Eternithaus still inspires.