In March, 1934, Modern Mechanix reported on an unusually ambitious plan to solve Manhattan’s traffic and housing woes. Norman Sper, a “noted publicist and engineering scholar,” proposed to “plug up” the Hudson River with a pair of dams at either end of the island. This would reroute the water around Harlem and the East Side, exposing the riverbed between New York and New Jersey. The resulting dry land, once filled in, would nearly double the city’s size and create a gold mine in future real estate. Sper called his vision “the world’s eighth wonder.” But, like most of the unorthodox infrastructure projects featured in Modern Mechanix, it never came to pass. Two years earlier, the magazine had suggested that a system of “belt trains”—large, ceaselessly operating conveyor systems—might soon become the foremost means of public transportation in the United States. Yet here we are in 2017, and New York can’t even keep its subways on the tracks.

The notion of an everyday world transformed by grandiose ventures is not, of course, exclusive to the nineteen-thirties. It has exerted a perennial popular appeal. Even today, daydreams of mile-high skyscrapers, subterranean parks, and buses straddling entire highways are often treated as hard news. Though they are rarely realistic, as either engineering proposals or as political solutions to urban problems, they strike an imaginative chord. And justifiably so: compared with damming the Hudson, the idea of, say, fixing and maintaining Manhattan’s aging sewer system seems like the definition of tedium. For some people, the city of tomorrow must be a spectacle, or it won’t be the city of tomorrow at all.

One of the most conspicuous recent examples of this phenomenon is the Hyperloop, a futuristic transportation network that, its adherents say, will send paying customers through vacuum-powered tubes at speeds of up to seven hundred and sixty miles per hour—from San Francisco to Los Angeles in under thirty minutes. The project’s preëminent spokesman is Elon Musk, the forty-six-year-old tech entrepreneur behind Tesla and SpaceX, who has seemingly restyled himself as the Jerry Bruckheimer of urban design. Besides championing the Hyperloop, Musk also founded the so-called Boring Company, based in L.A. Its breakthrough concept? To put cars in semi-automated tunnels beneath the city’s traffic-clogged streets.

While Musk’s signature ideas—instant cities on Mars, families roaring coast to coast at the speed of sound—are generally indistinguishable from those of an uncle who has watched too much “Dr. Who,” he benefits from a media primed to record his every musing. Indeed, he launched a thousand hot takes when he tweeted, last week, that he had “received verbal govt approval” to begin digging tunnels along the Eastern seaboard. So unwavering is this attention that it has spawned a parody Twitter account, @BoredElonMusk. Bored Elon suggests occasionally funny, absurdist products and services—a “TV that automatically turns on subtitles when it recognizes by your facial expression that you’re having troubling hearing dialogue”—but the joke seems to be that these farcical speculations barely differ from ideas like the Hyperloop.

Still, the trouble with the Hyperloop is not its breathless gee-whizzery. It’s the fact that it mistakes the charismatic mega-project for a viable solution to current problems. If the Hyperloop’s purpose is to address large-scale urban mobility, then there are many other options already deserving of public funding and attention—ones that do not require a hard rebooting of the entire urban world to be realized. We could increase funding for Amtrak. We could make our existing subways run on time, safely. We could fix our bridges. If boredom is already setting in, recall the fate of the Concorde. We once lived in a world that boasted a supersonic airliner, capable of whisking passengers from New York to London in three and a half hours—but this was a very qualified use of the word “we.” Who exactly could book a ticket on the Concorde was determined entirely by wealth, and, as such, that now lost transatlantic wormhole never felt particularly futuristic. Certainly, it failed to revolutionize international transportation for the masses. Today, it’s as if this feat of aeronautical engineering never existed.

In the architectural world, a common insult is to denigrate a project—even a person’s entire professional output—as being mere “paper architecture,” just renderings and spatial fairy tales. From the avant-pop utopias of Archigram to the fractured existentialism of the conceptual designer Lebbeus Woods, architects who don’t really build anything are often dismissed as somehow impotent. They’re just doing it for themselves, the argument goes, not for the future; they’re drawing, not contributing. Yet, as with much of what Musk has proposed in the past few years, the Hyperloop is most interesting when seen precisely as this—a conversation-starter, a provocation. Paper architecture. Musk’s visions are valuable because they show that even people far outside the field of urban planning can be frustrated with the world others have built for us. They, too, should have a say.

Perhaps the appropriate response is to think of this in the register of science fiction. Sci-fi has always offered visions of alternative realities that bear a symbolic power or analytic weight, yet many of the most resonant fictional worlds would be catastrophic if physically realized. Think of Margaret Atwood’s alt-Earth dystopias, Rupert Thomson’s United Kingdom forcibly divided into quadrants based on emotional temperament, or even the world of “The Purge,” in which state-sanctioned violence keeps crime rates low. These creations succeed, so to speak, without being turned into flesh and steel. We don’t need to witness firsthand the horrors of “The Handmaid’s Tale” to learn from that novel’s political divisions. The same might be said of a pneumatic tube flinging you and your loved ones over the San Andreas Fault.

In a lecture several years ago at the University of Southern California, the architect Rem Koolhaas suggested that the city of Dubai had reached a logical dead end. By locking itself into the premise that every new building had to be a unique formal or structural experiment, he argued, Dubai had become not a paradise for ambitious architects and their engineers but something more like a series of ever-louder action films. The city’s unusual skyline of bleeding-edge, high-tech towers had, according to Koolhaas, lost any sense of calibration. There was nothing with which to compare these buildings—no base level, no zero point. They were deviations without reference. The end result was a meaningless mess of super-projects whose only real context was the global investment portfolios of the people who paid to construct them.

The risk of taking every billionaire’s quirky visions at face value is that the entire world might soon become like Dubai—a mash of incompatible, proprietary infrastructures, run by the private sector, with no larger coherence or goal. It’s great set design, but terrible city planning. Tunnels might abruptly end where investors fear to tread; driverless cars might be blocked from crossing bridges managed by rival tech firms. As for the Hyperloop, it is a P.R. coup for Elon Musk—and a project that, if realized, would undoubtedly be a thrill to experience. But it is by no means the solution that most people have been waiting for, other than the journalists wondering what story they might cover next.