In March, a design competition to “re-conceptualize” the U.S.-Mexico border wall set off controversy. “Why improve on a bad idea?” asked Vicki Gaubeca, an expert on border rights. “With all the accoutrements that you want to put on that wall, it’s still a wall, and it’s not a bridge.” As I wrote in 2009, in my then-column in Architect magazine, a border wall makes no sense: “Even children and seniors can scale it easily, and those who can’t simply funnel through the gaps, rerouting rather than preventing the flow of traffic… If the boundary doesn’t function, costs a lot, looks terrible, upsets communities, and damages ecosystems, why are we building it?”

Now Donald Trump is the last man standing in the Republican race for the presidency, and the border wall is the centerpiece of his platform. “Nobody builds walls better than me, believe me,” Trump insists. Yet, for anyone eager to establish a gated nation, is any wall sufficient? In the three decades that the Berlin Wall was up, an estimated five thousand people safely traversed it. (Another thousand were killed and 75,000 were imprisoned.) Trump’s wall would extend 2,000 miles, horizontally, from the Pacific to the Gulf of Mexico; vertically, it could be as low as a few times his own height. Fences don’t enclose land, they divide it; what’s on either side is open to the heavens.

A “big, beautiful wall” isn’t enough: what Trump really needs is a big, beautiful roof.

What if the entire continent were covered in an enormous vegetated roof of native grasses? Amber waves of grain, where buffalo roam from sea to shining sea. Make America great again—by returning it to its wild state.

A bit much? Yes, this might be beyond even Trump’s grand ambitions. Besides, while “nobody builds walls better,” maybe somebody does roofs better. A more modest approach would be to round everyone up in a smaller area—a sort of reverse internment. No need to close out Mexico if America is closed in. Designer Shane Keaney once calculated that if the entire population of the U.S. lived with the density of Brooklyn, all 300 million of us would fit in an area the size of New Hampshire, the fifth-smallest state. If the area were square, it would measure about a hundred miles wide, and you could ride a bike to the other side in a day. Writes Keaney, “We’d all be neighbors.” All of us Americans, at least. Roof that over, and we’d all live in a gigantic Costco.

Mass migration presents some logistical challenges, to say the least, and bringing everyone together also wouldn’t solve Trump’s core concern. By his tally, 11 million undocumented workers have infiltrated the U.S., and he promises to deport them once he’s president—a plan that failed in the 50s. A more reliable approach might be to separate only those Americans who want to live separately. According to polls, 84% of Trump’s estimated 10 million supporters favor his border policies. Why not isolate those 8.4 million people in a city of their own? Many Trump devotees live in mobile homes, so the mobility of home is already a familiar concept. Imagine a new metropolis the size of Chicago, created solely for 2% of Americans to escape the undesirables among us. Call it “Xenophobopolis.” Or simply “Trumptown.”

We’ll call it “Trumptown.” To separate them sufficiently, a walled compound won’t do. They’ll still need a roof to keep interlopers from above. The most efficient way to do it. A really, really big dome.

To separate them sufficiently, a walled compound won’t do. They’ll still need a roof to keep out interlopers from above. The most efficient way to do it? A really, really big dome. In “A Case for a Domed City” (1960), Buckminster Fuller proposed a two-mile-wide dome over midtown Manhattan. The geodesic dome, for which Fuller became famous, encloses the largest volume of interior space with the least amount of surface area. He calculated that his domed city would weigh only four thousand tons and could be installed by a fleet of helicopters in only three months at a cost of $200 million ($1.6 billion in today’s dollars). At five times the size, Trumptown could cost $8 billion, a steal compared to the $25 billion estimated for the planned border wall. Fuller claimed the Manhattan dome would reduce the city’s winter heat losses fiftyfold, and the dramatic energy efficiency of the Trump dome ironically would alleviate climate change, which the candidate has dismissed as “bullshit,”  a “hoax,”  “created by and for the Chinese.” Under the dome, there would no need to acknowledge climate, much less climate change.

To house eight million people at the density of Trump’s hometown of New York would require a dome ten miles in diameter—the estimated size of the domed reality-TV setting in Peter Weir’s The Truman Show (1998). Filmed on location at Seaside, Florida, the New Urbanist playground on the Gulf of Mexico, the story involves a megalomaniacal creator (“Christof,” played by Ed Harris) manipulating the life story of everyman Jim Carrey. In the Trump-man Show, The Donald would play both roles, the orchestrator and occupant of his utopia under glass.

In Under the Dome, Stephen King’s 2009 novel adapted into a popular CBS television series, extraterrestrial children drop a dome over a New England town—just to play a game. “We’re under the dome,” King has said of his story. “All of us.” Trump’s dome, a self-imposed human terrarium, would provide safe haven from terrestrial aliens. Another, much earlier novel, William Delisle Hay’s Three Hundred Years Hence (1881), envisions most of humanity living in glass-domed cities under the sea, partly to escape the “inferior” races. Domed cities have a long history of isolationism.

The Wall Street Journal has pinpointed the “place that wants Trump most” as Buchanan County, Virginia, where 70% of voters support him. “He talks before he thinks,” one resident told a reporter, “so he doesn’t have time to think up something and lie to you.” Named for James Buchanan, considered by historians the worst American president because of his failure to prevent the Civil War, this seems the perfect home for the Trump dome, nestled in the Ridge-and-Valley Appalachians, right at the border of West Virginia, the “most racist state,” according to Twitter.

The UAE is planning “the world’s first climate-controlled domed city,” a 48-million-square-foot mall complex.  Can Trump beat Dubai in the dome race? “As long as you are going to be thinking anyway,” he has said, “think big.”