Monumental victims of dwindling finances, public backlash and political roadblocks, many designs from the world’s most celebrated architects never broke ground. Promising much in their form and magnitude, the stunning structures exist only as colorfully rendered visions on a lost landscape. Here, man’s best unmade plans.

In his classic novel “Invisible Cities,” Italo Calvino envisioned a building, in a city called Fedora, containing a series of small globes. The visitor peering into each would see a small city, a model of a different Fedora. “These are the forms the city could have taken,” wrote Calvino, “if for one reason or another, it had not become what we see today.” In the real world, one can stand on a street in Manhattan and look into one’s iPhone, where the app “Museum of the Phantom City: Other Futures” reveals the New York that might have been: from the fantastic (Buckminster Fuller’s projected Midtown-covering dome) to the nearly realized (Diller and Scofidio’s Eyebeam Museum).

Architectural history is told by the victors, city skylines their monuments. But there are also missing monuments, those projects which, by dint of political folly, the capricious tides of public taste or simple financial overreach, never break ground. The credit crisis, for example, has turned a presumptive architectural fantasyland in Dubai, that emirate of excess—where submerged hotels or $3 billion cities in the form of chessboards were the order of the day—into a graveyard of gauzy renderings.

The financial collapse claimed so many schemes that the architectural and design provocateurs Constantin Boym and Laurene Leon Boym, known for their small metal replicas of such buildings as the Chernobyl plant (as part of the “Buildings of Disaster” series), began in 2009 to produce a series of so-called “Recession Souvenirs,” projects like Norman Foster’s Russia Tower. “But the series was short-lived,” says Constantin Boym, speaking from Doha, Qatar. “There was not much enthusiasm in this black humor any more.” (The few that were made, however, are highly collectible.)

As is suggested by their difficulty in getting built, unbuilt projects are often superlative in some sense, as much a statement as an edifice. Boris Iofan’s neoclassical Palace of the Soviets, for example, on which construction began in 1937, gradually morphed (with input from Stalin) into what would have been the world’s largest skyscraper. War intervened, however, and its steel frame was repurposed into bridges in 1941.

Even when absent, unbuilt projects can exert a curiously powerful hold on the cultural imagination: Étienne-Louis Boullée’s massively spherical 18th-century cenotaph for Isaac Newton still looms, like the Montgolfier balloon that was said to have inspired it, over the architectural landscape. The 1960s British proposal by Cedric Price for his Fun Palace, with its visual echoes in the Centre Pompidou, now looks prophetic.

Perhaps the most common, and salient, feature of unbuilt projects is that every architect, at some point in his career, will design one—or several. Will Jones, author of “Unbuilt Masterworks of the 21st Century,” says these are not necessarily negatives in an architect’s career. “If an architect can look back upon it without too much bitterness, it’s the perfect area to test out ideas,” he says. “It’s a proving ground, that they take on and can use in future buildings.” Jones notes that Richard Rogers’s Welsh Assembly building, for example, contains ideas from his unbuilt Rome Congress Center design, which itself, the firm notes, advanced themes from a competition for the Tokyo International Forum project.

The building itself hardly sailed to completion; Rogers was briefly fired from the project. But he ultimately avoided the fate of Zaha Hadid, whose Cardiff Bay Opera House, one of the most lamented unbuilt projects of the past few decades, crashed amid the rocky shoals of politics—nationalist, classist (The Sun denounced using Lottery funds for a project for “Welsh toffs”) and aesthetic. “It devastated us,” Hadid says. But this, and a subsequent slew of unbuilt competition entries, “tested our ideas on landscape topography, and you can see the results of this now in all of our work.” Hadid may be the only architect with two unbuilt opera houses (a project in Dubai was terminated), not to mention a celebrated—and built—opera house in Guangzhou, China.

Sometimes unbuilt projects turn out to have a rather unexpected second life. The young Danish architect Bjarke Ingels, whose firm designed the Danish Pavilion at the Shanghai World Expo, entered a competition in 2008 for a resort project in the north of Sweden. The firm lost the competition. But when they showed the work to a Chinese developer, he was struck by the fact that the building’s shape resembled the Chinese character for “people.” The firm hired a feng shui master, scaled the building up to “Chinese proportions,” and the “People’s Building” is now slated for Shanghai’s Bund.

With China’s expanding economic might, its low-cost labor, and relative lack of restrictions in blank-slate cities like Guangzhou, unbuilt projects have been a rarity. This is common in places where economic booms and cultural dreams conspire. As Los Angeles Times architecture critic Christopher Hawthorne argues, “Los Angeles was known for much of the 20th century as the city where anything—and everything—could and did get built, from massive subdivisions, to avant-garde houses clinging to hillsides, to hot dog stands shaped like hot dogs.”

On the flip side, however, sits another kind of “unbuilt” architecture—that which is torn down. And Los Angeles, Hawthorne says, rarely paused to reflect as it knocked down iconic architecture. Today, he says, with open land more scarce, seismic and other building codes constricted, it’s much harder to get things built. So now, as it is elsewhere, the destroyed and the unbuilt jostle in the collective imagination, and, as Hawthorne describes it, “the black-and-white photograph of the long-ago destroyed landmark is now joined in the collective imagination by the sleek digital rendering of the high-design project that couldn’t get financing.”

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