I use that term advisedly: "Supertall" is a category of building defined by theCouncil on Tall Buildings and Urban Habitat as between 984 feet and 1,968 feet in height. (Anything much taller than that is, technically speaking,"megatall," and not permitted in the U.S. by the Federal Aviation Administration.) The SHoP Architects project in Midtown—111 West 57th St.—is not only a giant at 1,350 feet. It's also strikingly narrow.

"The majority of the shear load is happening on the east and west façades," Chakrabarti explains, referring to one of the fundamental forces that architects and engineers have to account for in designing buildings. Those façades will boast another bravura element of the design: a system of terra-cotta blocks.

Even in Billionaires Row—where Midtown zoning allows skyscrapers to soar—the oxygen has mostly been used up. To build the towers that are rising now, in many cases, developers purchased air rights from adjacent shorter buildings. "At least in this corridor, most of the air rights have been used up," Chakrabarti says.

In other words, these superskinnies are unique—a "registration of the market," as Chakrabarti calls them. "It is a typology that’s happening, no question," he says, noting that SHoP has at least two more supertalls coming to New York. "But if I look at our overall portfolio, [superskinny, supertall] is not an enormous percentage in terms of square footage."

So fans and critics of these buildings shouldn't expect to see them copied everywhere. At least, not until design and engineering technology advances to the point that that the aspect ratio can be pushed to even leaner proportions in markets that could sustain these developments. Or, not until other markets generate the political climate that makes these developments possible.

Wait, I'm missing the main reason. Is it air rights?

Yes, that is the case in the U.S.