Architect Jean Nouvel has designed an implausibly thin obelisk that would rise in crooked facets almost as high as the Empire State Building.

Thank New York zoning laws for this chic behemoth, which could cast some of Midtown’s most prized and densely built blocks into darkness. Someday such abuse may become illegal.

The 75-story hotel and condo would be wedged between the Museum of Modern Art and 1330 Sixth Ave., a drab corporate tower typical of the 1960s. It’s meant to rise to more than twice the height of nearby Museum Tower, which MoMA built in the 1980s, and will define a whole new scale in the neighborhood.

Its 1,200-foot (365-meter) height would cast MoMA’s sculpture garden into almost perpetual shadow. Perhaps that’s fitting, since MoMA sold the 17,000 square foot lot to developer Hines for $125 million a year ago. The deal allows the museum to add 50,000 square feet spread over three levels of the new building.

The real art in this deal, however, is the zoning. When MoMA Director Glen Lowry started talking up the sale, he said the site would support a development of about 210,000 square feet. Although much about the mix and final size of the building is still being worked out, a size greater than 500,000 square feet is bandied about.

How does Hines do it? Company officials wouldn’t explain except to say that the buildable square footage already has been legally established. Exactly how it’s done won’t be publicly known until Houston-based Hines files for a required special permit, which it intends to do early this year.

The building’s height is mainly accomplished by a zoning device called transfer of development rights. This allows unbuilt space to be moved from above nearby landmark structures to Hines’s site.

That said, Mr. Nouvel, who designed the 40 Mercer condominium in SoHo with Hines and Andre Balazs, offers up a glittering image of Manhattan in the comic-book image of Gotham.

Instead of opening onto a lobby, visitors cross a bridge suspended dramatically over sunken restaurants and bars. In what Hines calls a “seven star” 100-room hotel, a spa pool slips between the dark diagonals of the building supports.

The zoning protects some daylight at the street frontages by requiring setbacks as the tower rises. In stacking some 120 condos in 53 floors atop the hotel, Mr. Nouvel bends and facets the surfaces to keep within the ever-narrowing, legally buildable envelope.

At most, one unit will fit in each of the super-luxe top 20 floors. Some will be united as duplex or triplex units to deliver enough useful space to justify the staggering (though not yet determined) prices.

Perched above Midtown, Mr. Nouvel’s aeries will offer endless panoramas on two or three sides of each room. Mr. Nouvel’s defiant coup de grace is to carry a skeletal spire above the penthouse to the point at which the planes of the setback lines meet.

For me, the trouble with Mr. Nouvel’s design is not so much its great height — those skinny high floors won’t block many views or much light — but the thick, looming, lower floors. It’s not even leavened by the wind-scoured plazas that gather a few puddles of welcome sun along Sixth Avenue. It extends a worldwide trend toward thin, super-tall buildings that mix residential and commercial uses.

I’m drawn to Mr. Nouvel’s imagery — the Hines tower could make an extraordinary impression on the skyline. Still, it’s time to stop the abuse of this zoning device in the latest race for the sky.

Mr. Russell is the American architecture critic for Bloomberg News.

How Does Hines Build So Big?

Exactly how Hines calculates its buildable area won’t be publicly known until it files for a required special permit, which it intends to do early this year. New York City zoning allows owners of officially landmarked buildings to sell “air rights” — space unbuilt that zoning would allow. These rights to build can then be moved to sites adjacent or across the street. St. Thomas Episcopal Church, which abuts MoMA on Fifth Avenue, may have offered rights which could move through the MoMA site to Hines’s “receiving” site.