On a Friday afternoon in September, a conclave of architects and real-estate executives gathers in a hotel conference room to look over plans for Manhattan’s largest remaining chunk of emptiness. Hudson Yards, the railroad depot that stretches from Tenth Avenue to the Hudson River, and from 30th to 33rd Street, barely registers on the mental map of most New Yorkers. Look down from a neighboring window, and you see only a pit full of trains hazed with their diesel fumes. The planners’ view, though, takes in sugarplum dreams of the city’s shiny next wing: an $800 million concrete roof over the yards, and above it the country’s largest and densest real-estate development: 12 million square feet of ­offices, shops, movie theaters, gyms, hotel rooms, museum galleries, and open space, and 5,000 apartments, all packed into 26 acres. In the first, $6 billion phase—scheduled for completion by late 2017—the tallest tower will top the Empire State Building, and even the shortest will have a penthouse on the 75th floor.

The people in the conference room can visualize that future in high-resolution detail. On the screen, digital couples stroll among trees pruned to cubical perfection. A chain of glowing towers garlands the skyline, and tiny figures stroll onto a deck hanging nearly a quarter-mile in the air. Architects discuss access points, sidewalk widths, ceiling heights, flower beds, and the qualities of crushed-stone pathways. You could almost forget that none of this exists yet—until one architect points to a lozenge-shaped skyscraper and casually, with a twist of his wrist, remarks that he’s thinking of swiveling it 90 degrees.

The Related Companies, the main developer of the site, has called this meeting so that the designers of the various buildings can finally talk to each other, instead of just to the client. I’m getting the first look at the details at the same time some of the participants are. Suddenly, after years of desultory negotiations and leisurely design, the project has acquired urgency: Ground-breaking on the first tower will take place in the coming weeks. There’s a high-octane crew in the room: William Pedersen, co-founder of the high-rise titans Kohn Pedersen Fox Associates; David Childs, partner at the juggernaut Skidmore Owings and Merrill; Elizabeth Diller, front woman for the cerebral boutique Diller Scofidio + Renfro; ­David Rockwell, a virtuoso of showbiz and restaurant design; Howard Elkus, from the high-end shopping-center specialists Elkus Manfredi; and landscape architect Thomas Woltz, the only member of the group new to New York real-estate politics. Their task is to compose a neighborhood from scratch.

The success of Hudson Yards depends on the question: Can a private developer manufacture a complete and authentic high-rise neighborhood in a desolate part of New York? “This isn’t just a project; it’s an extension of the city,” says Stephen Ross, Related’s founder and chairman. New York has always grown in nibbles and crumbs, and only occasionally in such great whale-gulps of real estate. In the richest, most layered sections of the city, each generation’s new buildings spring up among clumps of older ones, so that freshness and tradition coexist. A project of this magnitude, concocted around a conference table, could easily turn out to be a catastrophe. The centrally planned district has its success stories—most famously, Rockefeller Center. Coordinated frenzies of building also produced Park Avenue, Battery Park City, and the current incarnation of Times Square. But this enterprise is even more ambitious than any of those, and more potentially transformative than the ongoing saga of the World Trade Center. New York has no precedent for such a dense and complex neighborhood, covering such a vast range of uses, built in one go.

That makes this Ross’s baby. Hundreds of architects, engineers, consultants, planners, and construction workers will contribute to the finished product. Oxford Properties Group has partnered with Related, and the city dictated much of the basic arrangement. But in the end, how tightly the new superblocks are woven into the city fabric, how organic their feel, and how bright their allure will depend on the judgment and taste of a billionaire whose aesthetic ambitions match the site’s expanse, and who slips almost unconsciously from we to I. “We went out and selected great architects and then created a whole five-acre plaza,” Ross says. “People will have never seen such a world-class landscaping project. I can’t tell you what that plaza will look like, but what I visualize is a modern-day Trevi Fountain. It’s going to be classical and unique.”

The best clue to what he has in mind isn’t in Rome, but at Columbus Circle. Ross lives and works in the Time Warner Center, which Related built, and if you imagine the complex blown out to five times its size, you begin to get a sense of what’s coming at Hudson Yards: crowds flowing from home to boutique, hotel to subway, office to spa, concert to restaurant—and all that activity threaded around and through a curving plaza equipped with fountains and a very tall monument, as yet unchosen. The Time Warner Center brought profitable liveliness to Columbus Circle, the once moribund, now vibrant hinge between midtown and the Upper West Side. But massive as it is, the Time Warner Center is dainty by comparison.

Start on the High Line, at West 30th Street near Tenth Avenue. At the moment, the landscaped section peters out here, but the old elevated railway continues, forking both east and west to form the southern border of Hudson Yards. Eventually, you’ll be able to continue your stroll beneath the canopy of an office tower housing the headquarters of the leather-goods company Coach. It’s a tricky spot, and the interaction of city street and raised park forces the architecture to perform some fancy steps. The building genuflects toward Tenth Avenue on muscular concrete legs. Coach’s unit reaches out toward the High Line, and the crown greets the skyline at a jaunty tilt. With all its connections and contortions, the tower, designed by Kohn Pedersen Fox, assembles its identity out of the complexities of city life. “My whole career has been about taking buildings that are inherently autonomous and getting them to become social gestures,” remarks Pedersen.

Head up a couple of blocks from Coach’s future headquarters, and at West 33rd Street, another KPF tower tapers from vast hoped-for trading floors to a jagged peak 1,300 feet up. A state-of-the-art office building these days requires huge open layouts and thick bundles of elevator shafts, which tend to give it the natural grace of a hippopotamus thigh. But look up: Here, the design artfully disguises the two towers’ bulk by making them seem dramatically foreshortened, as if they were speeding toward the sky. One slopes toward the river, the other in the direction of midtown, parted like stalks of corn in a breeze. The cone of space between them draws sunlight to the ground and leaves a welcome break in the city’s increasingly crowded skyline. With any luck, you should be able to stand at the foot of these towers and feel sheltered but not squashed. It would have been far easier to wall the development off and let each tower stand in isolated splendor. Instead, planners have tried to soften the borders of their domain. That’s not just civic-mindedness; it’s good business. If Hudson Yards is going to be a truly urban place, it will have to lure people who neither work nor live there but who come because everyone else does. The development will have two major magnets, one for commerce, food, and entertainment, the other for that primal necessity of New York life: culture.

Related is pinning a lot of financial optimism on a five-floor, two-block-long retail extravaganza that links the two KPF towers, rather like the Time Warner Center shops, only bigger, busier, sunnier, and more tightly knit to the city. “We don’t want this to feel like a mall,” insists its architect, Howard Elkus. Pedestrian passageways cut through the building, extending the streets indoors, and a succession of great glass walls turn window-shopping into a spectator sport. The liveliness engine is on the fourth floor, where a collection of informal but high-end food outlets curated by Danny Meyer looks out over the central plaza—“Eataly on steroids” is how one Related executive describes it. Above that are more expensive restaurants and a ten-screen multiplex.

Stroll out the western side of the shopping center toward the central plaza, walk diagonally across to 30th Street, halfway between Tenth and Eleventh Avenues, and you come to the most intriguing and mysterious element of Hudson Yards: the Culture Shed. Having set aside a parcel of land for cultural use, the city put out a call for ideas. Elizabeth Diller and David Rockwell answered with an amalgam of architectural and institutional innovations: a flexible gallery complex to accommodate traveling exhibits and nomadic performing events. Together, they designed an enormous trusslike shell that could fit over the galleries or roll out like a shipyard gantry to enclose a vast performance space.

The city refuses to discuss architectural details, how the still-theoretical organization will function, or who would pay to build and operate it. But it’s easy to imagine it being used for film premieres and high-definition broadcasts from the Metropolitan Opera or as a permanent home for Fashion Week, which now camps out in tents. The Culture Shed can give Hudson Yards the highbrow legitimacy and cutting-edge cool it needs to become an integral part of New York, and also create a cultural corridor running from the Whitney Museum at Gansevoort Street (now under construction), through Chelsea’s gallery district, and up to Lincoln Center. The project may be in the wishful-thinking stage—it could still get scaled back or dumbed down, or it could vanish altogether. But it does have one crucial booster: the Related Companies. “The Culture Shed is critically important,” says Jay Cross, the executive who is running the Hudson Yards project. “We’re going to be major supporters because we want and need to see it come to fruition.”

Hudson Yards is getting much more from the city than just the Culture Shed. While planners keep working out ways to weld the complex to its environs, the West Side has already begun to embrace its coming addition. New rental towers have sprouted in the West Thirties and burly office buildings will soon rise along Ninth and Tenth Avenues. “There are communities around us—Hell’s Kitchen, Midtown South, West Chelsea, New Jersey to the west—that if we do a great job are just naturally going to flow in and populate that space,” says Cross.

The site as a whole is a yawning pit, not so much a blank slate as an empty socket, surrounded by amenities and infrastructure just waiting to be plugged in. Hudson River Park runs along the western edge (set off by Twelfth Avenue), the High Line spills in from the south, and the future Hudson Park and Boulevard will swoop down from the north. The No. 7 subway-line extension is on the way to completion, the Javits Center is being overhauled, and maybe one day Moynihan Station will even get built. In all, $3 billion in taxpayer-funded improvements encircle the Related fiefdom—not including city tax abatements. “Where else have you ever seen this kind of public money for infrastructure to service a whole new development, in the heart of the city, with that much land and no obstacles?” Ross asks. His vocal enthusiasm for Mitt Romney and the Republican Party’s small-­government credo evidently hasn’t curbed his appreciation for public support.

Although it’s the next mayor who will cut the first ribbon, in the long run Hudson Yards may well be the grandest and most dramatic piece of Michael Bloomberg’s legacy. It’s been on the city’s to-do list for almost a decade, ever since Bloomberg hoped to draw the 2012 Olympics to New York with promises of a West Side stadium. The fact that London won the games was a disappointment to him but a stroke of luck for the West Side, scuttling what would have been a disastrous stadium plan, while at the same time calling attention to the value of the real estate above the tracks. Eager for space to put up high-rises and now prompted by a big hole on Manhattan’s western flank, the city focused on a rezoning that is gradually pulling midtown’s center of gravity westward.

There are two ways to conceive such a monster project. One is for a single architectural overlord to shape the whole shebang, as Raymond Hood did at Rockefeller Center. Steven Holl, whose offices overlook Hudson Yards and who has designed two similarly gargantuan complexes in China, submitted an entry that might have resulted in a work of thrilling coherence, with the same sensibility imbuing every detail, from door handles to office blocks. But the auteur development also risks yielding a place of oppressive uniformity, where each aesthetic miscalculation is multiplied many times over.

Related chose the second option: recruiting an ensemble of brand-name designers. That approach emulates a sped-up version of New York’s gradual, lot-by-lot evolution; the danger is that it can produce a jumble. “Sometimes architectural vitality leads to messiness, or varying degrees of quality, and we’re trying to avoid that,” acknowledges Cross. “Every building is going to be best in class. That’s the common thread.”

But bestness is not actually a unifying concept, and when the city held the competition to award the development rights in 2008, the Related entry failed to wow the city, the public, or the critics. “With a drop-dead list of consultants, contributors, collaborators, and anyone else who could be thrown into the mix … [the company] has covered all possible bases with something dreadful for everybody. This is not planning, it’s pandering,” wrote the critic Ada Louise Huxtable in The Wall Street Journal. None of that mattered: The project originally went to another developer, Tishman Speyer, and when that deal fell through, Related scooped it up. Architecture had nothing to do with it.

Yet nearly five years later, with contracts signed and money starting to flow, that gold-plated crew of designers, working in separate studios, with different philosophies and, until recently, little consultation, has nevertheless produced a kind of haphazard harmony. What unites them is their taste for complexity and the deftness with which they maneuver conflicting programs into a single composition.

Just past the Culture Shed, on the 30th Street side of the site at Eleventh Avenue, is the eastern half’s only purely residential tower, designed by Diller Scofidio + Renfro, with David Rockwell. It’s an architectural griffin, grafting together rectilinear rental units on the lower floors with flower-petal condo layouts up high—about 680 apartments in all. The fantastically idiosyncratic bulges and dimples join in complicated ways that make the glass façade look quilted. Now walk north, back across the plaza and past a still-to-be-designed café pavilion, and you come to another tower with a textured exterior—vertical folds with stone on one side and glass on the other, as if a palazzo had merged with a modernist shaft. Actually, the building is even more hybridized than that. David Childs, the architect of the Time Warner Center and One World Trade Center, had to shoehorn a large Equinox gym plus offices, an orthopedic hospital, a sports emporium, a hotel, and a condominium into a curved base and a slender tube. “Hudson Yards is a city within a city. This tower is a city within a city—within a city,” he says.

The most delicate, crucial, and treacherous design problem at Hudson Yards isn’t a building at all but the public space, and especially the five acres in the middle, an expanse about as large as Bryant Park. Done right, it could be the most vibrant gathering spot on the West Side, a New York version of Venice’s Piazza San Marco. Done wrong, it could be a windswept tundra populated only by office workers scuttling between the subway and their desks. It’s worrisome that Ross and his team postponed thinking about that void until so much of the architecture had been designed, but heartening that they are intensely focused on it now. Related has given the job to the talented Thomas Woltz, whose quietly refined restorations of gardens and college campuses may not quite have prepared him for the fierce pressure of shaping New York’s most ample new public space.

It’s not just a place for people to mingle but for the relationships between the various buildings to express themselves across the connecting plaza. “One of the paintings I admire most is The School of Athens,” says KPF’s William Pedersen, referring to Raphael’s klatch of bearded philosophers chatting beneath noble vaults. “You have great historical and intellectual figures gathered together in dynamic groups of interchange, gesturing to each other. That’s the architectural assignment for each of us.”

David Childs phrases a similar thought in a way that graciously defers to Woltz even while sending the message: Don’t screw this up. “We have an obligation to create great architecture, and all the buildings have to be related to the space in the center,” he says. “The void is the most important part.”

Woltz has gotten it wrong once. In his first presentation, he placed a plush lawn at the center of the complex, and Ross nearly kicked him out of the room. What Ross wants is not a place to toss a Frisbee, but a town square alive with purpose and electricity. That’s a spectacular challenge; there are few great models for a European-style piazza within a ring of skyscrapers. For now, Woltz’s solution is a paved ellipse, outlined by a perimeter of trees cultivated with geometric severity—given “the Edward Scissorhands topiary treatment,” as one designer puts it. The idea is to create a verdant transition from the human scale to that of glass-and-steel giants. “In an open space next to 1,000-foot towers, our tallest tree is going to be like an ant next to a tall man’s shoe,” Woltz says.

But the most maddening paradox of Woltz’s assignment is that he must tailor an open space to the motley public—in ways that will please a potentate. Like some fairy-tale monarch, Ross has dispatched his counselors to find an artist capable of supplying his modern Trevi Fountain. What he wants is something monumental enough to focus the entire project, a piece that’s not just watery and impressive but so instantly iconic that people will meet by it, shoot photos of it, notice it from three blocks away, and recognize it from the cover of guidebooks. You get the feeling that Ross is hedging his bets: If Woltz can’t deliver a world-class plaza with his trees and pavers, maybe a Jeff Koons or an Anish Kapoor can force it into life with a big honking hunk of sculpture. A giant puppy can’t solve an urban design problem, though. It’s nice that a hardheaded mogul like Ross places so much faith in the civic power of art, but he may be asking it to do too much.

The plaza is the node where the site’s conflicting forces reveal themselves: the tension between public and private, between city and campus, between democratic space and commercial real estate. Occupy Wall Street’s takeover of Zuccotti Park last year pointed up the oxymoron inherent in the concept of privately owned public space: You can do anything you like there, as long as the owners deem it okay. Childs hopes that his client’s insistence on premium-brand design won’t make Hudson Yards just the province of privilege. “We want this project to be laced through with public streets, so that everyone has ownership of it, whether you’re arriving in your $100,000 limo or pushing a shopping cart full of your belongings.”

The plans include drop-off lanes, so the limos are taken care of. But if the shopping-cart pushers, buskers, protesters, skateboarders, and bongo players start feeling too welcome at Hudson Yards, Related’s security guards will have a ready-made ­argument to get them to disperse: This is private property.

Atop the 1,300-foot office tower, soon to rise at 33rd Street and Tenth Avenue, by Kohn Pedersen Fox Associates. Photo: Rendering by Visualhouse

Unnumbered buildings (the western half of the development) have yet to be designed. Photo: Map by Jason Lee

The view from the High Line. Photo: Rendering by Visualhouse

Photo: Rendering by Visualhouse

Photo: Rendering by Visualhouse

Photo: Rendering by Visualhouse

Photo: Rendering by Visualhouse

Photo: Rendering by Visualhouse

Photo: Rendering by Nelson Byrd Woltz

Photo: Rendering by Nelson Byrd Woltz