The habitable bridge is making a comeback in urban planning.
The answer to one of today's most difficult urban planning problems may lie in the Middle Ages. In cities and towns across America, freeways cut through communities, creating urban dead zones that sever neighborhoods from each other. To heal that damage, the city of Columbus, Ohio built a type of urbanized bridge that was common in Europe between the 12th and 17th centuries.
In Medieval and Renaissance Europe, imaginative, multifunctional bridges known as "habitable bridges" were quite common. Some hosted markets. Others contained mills that harnessed the power of the river. Many housed defensive towers or featured chapels. Beyond the novelty of having buildings on a bridge, they were highly functional, as they became natural venues for commercial trade. Perhaps the most famous habitable bridge was London Bridge, which had buildings on it from 1209 until it was rebuilt in 1831. Other surviving habitable bridges include Ponte Vecchio in Florence, Italy; Ponte di Rialto in Venice; and Krämerbrücke in Erfurt, Germany.
By the 18th and 19th centuries, the construction of habitable bridges was phased out in Europe as the disciplines of architecture and engineering became divorced. "Bridge engineers have never been attracted by the idea of encumbering their work with structures deemed by them to be parasitical," writes Jean Dethier in his book Inhabited Bridge: Past, Present and Future.
This style of bridge never caught on in the Untied States. However, habitable bridges have captured the imagination of several American architects, including Raymond Hood, who in 1925 penned an article for The New York Times Magazine describing a 10,000-foot-long bridge whose support pylons would be made of several 50- or 60-story-tall residential skyscrapers. More recently, famed architects like Rem Koolhaas and Bjarke Ingels have created plans for ambitious habitable bridges, but most have never made it off the drawing board.
Why should contemporary bridges need to do more than simply transport people or freight from point A to B? Dethier offers his take: "The inhabited bridge provides a continuity within the urban fabric that is not only social and economic but also cultural, emotional and symbolic at a point where a natural break would otherwise exist," he writes. "Indeed, it is both seductive and functional."
That brings us back to Columbus. In the late 1960s, a major highway (now Interstate 670) was built through town, carving a 200-foot-wide gash in the city that separated downtown Columbus from the nearby Short North neighborhood. A plan for capping the highway was developed in 1996, and finally completed in 2004. Technically, the project consists of three connected bridges: Car traffic passes on the middle span, flanked on either side by platforms that support storefronts and sidewalks. The three bridges fit together into one urbanized overpass that's home to a handful of restaurants and shops, all of which turn their backs on the highway. "I think the success of it is that most people don't even know they're on a bridge," says architect David Meleca, who designed the retail portion of the project.
Meleca says one of the models he looked at when drawing up plans for the High Street cap was Ponte Vecchio, a more than 600-year-old bridge in Florence with three floors of shops resting on it.
Although they share a common feature, there's a major difference between a bridge that crosses a river and one that spans an eight-lane highway. Whereas the habitable bridges of Europe crossed some of the continent's most important rivers, which were often at the center of urban life, the bridges that pass over modern highways them aren't typically thought of as prized real estate. And as the Chicago Tribunenoted in a recent review of the Columbus project, many American cities have an oversupply of retail space.
Meleca acknowledges that a bridge like his might not work for every highway crossing, but on High Street, renting the space hasn't been a problem so far. "It's added a really strong connection with the downtown," says Meleca. "Before the bridge was done, you would've never walked across that freeway. It was a typical utilitarian, scary freeway crossing." Extending the urban streetscape across the highway shields pedestrians from the roar of the road below and lifts a psychological barrier between neighborhoods, healing a generation-old wound created by the Interstate Highway System.
See a slideshow of habitable bridges past, present, and future.