There’s no shortage of grand gestures in high-profile buildings tailored like a bespoke suit for a specific client and function. Once the original tenant moves out, however, the structures are often gutted—which is expensive—or demolished—which is taxing on the environment. In designing Rotterdam’s new city hall—dubbed the Timmerhuis—the Office for Metropolitan Architecture opted for a multi-purpose approach. Intended to be future-proof, the pixelated mixed-use structure can morph over time, demonstrating a new paradigm for sustainable urban design.

The 521,000-square-foot building holds Rotterdam’s municipal offices, a museum, retail spaces, a cafe, and 84 apartments. Predominantly slick glass and steel, the new structure is fused with the existing 1953 city hall. A soaring atrium cuts through the center of the building and there’s parking below ground. It’s a veritable city within the city. And thanks to its ambitious sustainability credentials—prefabricated steel framing, energy storage systems, solar panels, shading system, and a car-sharing program—Timmerhuis has achieved an “excellent” rating from BREEAM, an international metric for green building.

But the real innovation is its mutability. “A good urban building can accommodate as many unforeseen events as possible,” architect Reinier de Graaf, a partner at OMA, says. To that end, the structure is relatively easy to retool. Unlike concrete—a favorite modern material—steel can be recycled. Moreover, the randomness of the silhouette all but ensures that additions won’t stick out like a sore thumb. The modular design looks like an unfinished stack of blocks. Should the client need to add to the building, it simply slots another block into the mass. The floor plan of the residences and offices are based off of squares and rectangles and because of this organization, one could be converted to the other relatively easily.

It’s the latest example of a building that attempts to grapple with questions of longevity. How can architecture’s shelf life be extended? How can a building respond to the times? Architect Jeanne Gang has adopted a plug-and-play approach, in which technologies can be moved in and out as new advancements are made. Building science and technology is moving fast. Designs are becoming more mutable in response.

OMA, the firm of Dutch starchitect Rem Koolhaas, won the commission for the Timmerhuis in 2009. The government wanted a building that could stand the test of time because the most sustainable building is one that can be used in perpetuity. OMA’s design seemingly fit the bill.

After the city awarded OMA the commission, competing firms filed a lawsuit, alleging that the design wouldn’t meet the minimum budgetary and durability requirements set forth. Ultimately, prefabrication helped OMA demonstrate that it wouldn’t exceed cost estimates because of the economies of scale of serial production. Total price tag of the building? 100 million Euro, or about $109 million.

“The whole project was built on an incredibly tight budget—which we had to keep—and that’s where the prefabrication of standard parts plays an enormously important role,” de Graaf says. “Anywhere in the western world, generally the cost of labor is larger than the cost of material. So if you save time rather than material, that has a very big cost impact. We have a steel building, massively spectacular cantilevers, and all of the features of a building that would be vastly over budget. Nevertheless, it isn’t.”

Timmerhuis’s structure was built like a kit of parts for the framework and facade treatments. “Normally you would assume that standardization leads to boredom, leads to a very redundant shape,” de Graaf says. “Here we have a combination of complete standardization and extreme variety. That’s in a way what the building tries to do—it tries to reconcile a number of phenomena which are often considered mutually exclusive.”

The contrast of expectations extends to the residential spaces. OMA incorporated generously sized rooftop terraces for the apartments, lending them a suburban sensibility despite their urban context. The apartments range in size from about 645 to 2,200 square feet and all have been sold.

“What we didn’t want to do was make the next grand statement with this building,” de Graaf says. “Rotterdam was bombed in World War II. Since then it has basically been an exhibition ground for every dominant architectural style, where each style is in a way an abrupt transition or denial of the previous. The cumulative result of all those U-turns is a city with a highly improvised look. We wanted to make a building that looked improvised, unfinished, and worked with an aesthetic of randomness. If it could operate at a certain level of coincidence, it could echo Rotterdam’s present state. Rather than tell the city how things should be done, we mirrored it. So the building is still the building, but it’s also an homage to the city of Rotterdam.”

If desirability is a yardstick for success, then Timmerhuis has overcome the first hurdle. But for de Graaf, the real test will be how people inhabit every square foot of the building, how they personalize the standardized backdrop, and how the building is embraced over time. When OMA proposed the structure, it was met with questions and doubt and perceived by some—like the three competing architecture firms who filed the lawsuit against the building—to be a risk. Since then, however, the firm has proven that the design and methodology worked. Potentially, it serves as a model for dense, mixed-use, sustainable urban development.

“If this building proves to be a success in terms of life that goes on it, it’s going to create its own demand,” de Graaf says. “Once the paradigm is built, once it’s proven, once it’s popular, [people] can’t get enough of them. The building might represent a pivotal movement where you move from skepticism to enthusiasm.”