"There have been something like 67 attempts to build on this site since 1965," says Ellen van Loon, the OMA partner who led the design of BLOX, a 290,000-square-foot, extremely mixed-use, thoroughly modern glass building that opened this month on the harbor in Copenhagen's historic center.

The difficulty lay in the heavily trafficked ring road that cuts through the site. OMA's scheme goes under and over the expressway, with five stories aboveground and five stories below, including four levels of fully automated parking. “Not every developer is willing to pay the extra money it takes to do that, but this client wants to invest in the public realm,” says van Loon.

The client, Realdania, is a Danish philanthropic group that supports projects in the built environment. Two of the main tenants at BLOX—the Danish Architecture Centre and BLOXHUB, an innovative office for sustainable development—do the same.

Besides exhibition spaces and offices for those tenants, the building also contains co-working spaces, a multilevel restaurant, a café, bookstore, fitness center, and 22 rental apartments, not to mention a playground. Its setbacks integrate large terraces for taking in waterfront views; its facade combines white fritted glass and a green glass that matches the deep green of the water, as well as panels of woven metal.

Inside is an arresting mix of dark concrete, black cork, warm wood, cool metal grating, smooth aluminum, and polished brass floors and walls (in what OMA calls the “golden room”). The interiors are arranged somewhat like a panopticon, where the central gallery offers glimpses into the rooms that surround it and vice versa. Similar views across stairwells and atria and through offices connect most spaces. “There's a lot of creative talent in this building,” says van Loon. “Seeing each other leads to collaborating.”