Fostering fancy apartments. (dbox/Zeckendorf Holdings)

Those Zecekendorfs sure do love their starchitects.

From William Zeckendorf's work with I.M. Pei and Minoru Yamaski in the 1960s and '70s to his grandsons' projects with the likes of  KPF and, most notably, Robert A.M. Stern, who created both the brand new 15 Central Park West and the newly renovated 18 Gramercy Park South, the Zeckendorfs have a thing for high design.

Add to that now 50 UN Plaza, a 44-story condo tower on the East Side that will be Lord Norman Foster's first residential commission in the United States. Mr. Foster is well known for his work on the Hearst Tower, World Trade Center Tower 2 and the new Sperrone Westwater Gallery on the Bowery, as well as a new commission for 425 Park Avenue for L&L Holdings. With this latest commission, he cements his place as an all-around architectural power in the city.

Tomorrow morning, Arthur and William Lie Zeckendorf, real estate scions like few others, will break ground on the project at 345 East 46th Street, on the corner of First Avenue. The location will afford the project prime river views, as well as a prominent place on the skyline right between the United Nations headquarters and the Trump World Tower. The Observer has obtained an exclusive rendering of the project, which shows a glassy building of in the high-tech vein for which Foster + Partners is best known.

More demure than buildings like Hearst or the so-called Gerkin in London, 50 UN Plaza seems to strike the proper balance of brash understatement the Zeckendorf's so seem to favor.

The project holds special significance for the Zeckendorf family, since they got their start at the United Nations. William Zeckendorf, Sr., assembled the land that Nelson Rockefeller than bought to build the United Nations complex, and Arthur and William Lie Zeckendorf's maternal grandfather was Trygve Lie, who served as the first secretary general of the United Nations.

A special announcement of a gift to the neighboring Daag Hammarskjold Plaza park is expected at the ground breaking, with Borough President Scott Stringer in attendance, as well as local Councilman Dan Garodnick and Eyal Ofer, head of Global Holdings and a partner in both 50 UN Plaza and 18 Gramercy Park South.

The project will include 87 units, ranging from one-bedrooms as large as 1,100 square feet to three bedrooms as big as 3,000 square feet. There will also be a number of full-floor residences twice that size, as well as a penthouse duplex measuring some 10,000 square feet. Like at 15 Central Park West, one of the marquee features will be a private driveway. It is Lord Foster's first American apartment tower, following on the success of work he did in Vancouver, at Jameson House, completed in 2004.

The development of 50 UN Plaza is expected to cost $500 million to build, with completion by the end of 2014. If it is even close to the success of 15 Central Park West, which sold $2 million worth of units when it first came on the market (and is worth probably twice that now given a gangbuster market for resales in the famed building), then the Zeckendorfs and their partners should have no problem making an easy return on their investment here.

It looks like have just wrested the crown of New York's most luxurious development back from Gary Barnett.

As The New York Times noted late last year, the store marks another sign of Columbus Circle's transformation:

The store, of course, will front on Broadway and not on Central Park West. The building's condo owners--including Denzel Washington, Sandy Weill and Norman Lear, as well as 15CPW's developers, William and Arthur Zeckendorf--will not have to mix with the shoppers below.

The Observer's Chris Shott will have more on the opening on Friday.

The Plaza Hotel, on the other hand, has had four such deals close for above $10 million in the last few months. These include the penultimate: In July, one still-unknown buyer spent $51.5 million on six apartments on the seventh floor—if it holds, it will resound as the single biggest apartment deal in New York City history. (Most of the Plaza's sales have been much less spectacular, some for under—gasp!—$2 million, meaning, in a strict competition of amounts, Fifteen wins so far.)

The Plaza and Fifteen Central Park West together represent the crest of a wave of luxury development in Manhattan that commenced shortly after the turn of the decade. Both have storied pedigrees—the Plaza was an iconic hotel in its past life, and some of it will remain a hotel post-condo conversion; Fifteen was built by the Zeckendorf brothers on the site of the Mayflower Hotel—and both were heavily marketed as pinnacles of luxury living.

And now both have prices that will reliably astound as sales continue to close throughout the fall and into next year. But there’s a difference.

The roster of buyers for Fifteen Central Park West is known to even the most casual real estate voyeur in New York—The Observer, for instance, broke the news of Mr. Weill buying in the building back in July; we just didn’t know the amount. Other notables who plan to buy include rock star Sting, actor Denzel Washington, Jeff Gordon of NASCAR fame, director Norman Lear, sportscaster Bob Costas, and the Zeckendorf brothers themselves, Arthur and William Lie.

In the Plaza, the buyers have been… um, no one you’d know—though, to be fair, these are people paying well above the average Manhattan home price of over $1,100 a square foot, so they must definitely be somebody. The New York Times suggested that developer Harry Macklowe might be the $51.5 million buyer--or perhaps the buyer behind another $50 million-plus deal there that's pending. Otherwise, the unfamiliar fans the flames of speculation about which notables might be eyeing the icon on Central Park South.

Central Park West—and Fifth Avenue on the park’s east—have always attracted the well-heeled and the well-known. The Plaza, in its day as a hotel eminence, did the same.

Perhaps what we’re seeing is a second act for the Plaza both enviable and disappointing, but ultimately democratic: In the age of the $50 million apartment, money really is the in; fame’s merely an exclamation point, nice if you have it. The simply riche—whether nouveau or ancien—have taken the Plaza. Will they one day, a generation or three from now, do the same at Fifteen Central Park West?

With reporting by Max Abelson.

Unit 7C has closed for $9.67 million, according to city records. The buyer, listed as Carolina Real Property LLC, took its time closing. The deal went to contract back in September 2005 and did not close until just a few weeks ago. The true identity of the buyer could not immediately be determined, but we're guessing it may be NASCAR star Jeff Gordon, who has lived in North Carolina and who is known to have been an early buyer at the condo.

Fifteen Central Park West is one of the most anticipated new developments in recent city history. Developed by Arthur and William Lie Zeckendorf, the two-tower spread with 201 condos should record nearly $2 billion in sales when all is said and done.

Over the past two years, several notables besides Mr. Gordon have gone to contract for the spreads that average over $3,000 a square foot, including hedge fund manager Daniel Loeb, who went to contract on a penthouse in November 2005 for a then-record $45 million. Other buyers in the Robert A.M. Stern-designed condo include musician Sting and his wife Trudie Styler, sportscaster Bob Costas, director Norman Lear, and actor Denzel Washington.

It all started with William Zeckendorf Sr., the real-estate mogul’s real-estate mogul, whose greatest fault lay in being years ahead of his time. He assembled the parcel on which the United Nations rose in 1947 and also built the Roosevelt Field shopping center on Long Island, the Century City complex in Los Angeles, and several urban-renewal projects in Philadelphia and Washington, D.C.

Then he went broke.

His son, William Jr., vowed to take fewer risks, and so he did, for a while—but then he too fell upon difficult times.

His sons, Arthur, 47, and William Lie, 48, have just put up the premier new residential building in Manhattan at 15 Central Park West: 35 elegant stories of limestone, plus a swimming pool, screening room and restaurant. The pair has grossed more than $1.6 billion in sales so far, including the highest price ever paid for a condominium in New York City: $45 million, for a duplex penthouse.

“Sales will reach $2 billion on a $1 billion cost,” Arthur Zeckendorf told The Observer. “Our strategy was to focus on the high end, because that is where we saw strength in the market today. If we saw strength in the West 30’s and the West 40’s, we would go there.”

The Zeckendorfs made a very expensive but tightly controlled bet on 15 Central Park West. They spent $400 million to buy into one of the city’s best neighborhoods and then built condominiums, which, once sold, would quickly let them pay off the loans—and then some.

The main challenge was selling those condos, and that they did handsomely: Four-fifths of the 200-odd units in 15 Central Park West have been sold.

Before 15 Central Park West went up, Arthur did two studies: one concerning the features that made the great New York City apartment buildings great (courtyards, for example), and another about the best kind of limestone to use. The answer: Indiana limestone. And so the Zeckendorfs clad their building in stone from the same quarry that supplied the Empire State Building.

“They are calmly rational,” said M. Myers Mermel, a real-estate investor and consultant who has done business with the Zeckendorfs. “They just go quietly about the things that they are doing and seem to be able to accommodate the changes as they happen.”

Contrast that manner with William Sr., whose company, Webb & Knapp, built $3 billion worth of commercial projects in the space of 20 years, and who cultivated an image as a dealmaker and tycoon. “He was a tall man who always wore a Homburg,” said Kent Barwick, the president of the Municipal Art Society, who was working as a copywriter in the same building that the senior Zeckendorf had his company in about four decades ago. “He had this two-story glassed-in lounge on the roof where he would take all manner of people: I.M. Pei, Jackie Onassis.”

“Big Bill” Zeckendorf liked transformative projects that forever altered the land around them. His most celebrated transaction was taking an option on 17 acres of slaughterhouses along the East River knowing that they must be valuable, even though he didn’t know why.

As his option came due and he faced losing his deposit, he saw a newspaper headline proclaiming that the city was about to lose the United Nations because it couldn’t find a place for the organization’s headquarters. Zeckendorf called Mayor William O’Dwyer, who got the Rockefeller family to buy the land for $8.5 million and then donate it to the U.N.

In 1965, Zeckendorf found himself unable to make the mortgage payments on an overextended empire and went bankrupt. It didn’t take long for him to start a new venture, however. He found a few partners and, as his first deal, convinced a publishing house to extend its lease. The publisher was game, but wanted Zeckendorf to write his memoirs in return. So he did.

His son, Bill Jr., worked for his father at the comeback firm, which he eventually took over. Bill Jr. is known for his unassuming character, and he had early success by reviving undervalued properties like the Delmonico and the Barbizon. Then he made a much bigger gamble as part of the Union Square redevelopment, building a massive condo complex at the southeast corner of the park and naming it Zeckendorf Towers, after his father. (Well, after himself, too.)

In the late 1980’s, he did World Wide Plaza, the full-block residential-office complex between 49th and 50th streets, on the west side of Eighth Avenue. To entice commercial tenants to that edge of midtown, the Zeckendorfs offered equity in the building, because giving away part of the building was better than paying the interest rates that a bank would demand if the project were built before any occupants had signed leases. Neither project fared well in the 1990’s slump, and Bill Jr. lost majority control of both. He retired in 1992 and, now 77, lives in Santa Fe, N.M., in a development owned by his second wife, a former ballerina. (His first wife was Guri Lie, the daughter of former U.N. Secretary General Trygve Lie.)

Arthur Zeckendorf says that he and his brother didn’t cultivate their current approach to the family business in order to avoid the risks that plagued their father and grandfather.

“I would say they have both been very successful developers,” he told The Observer. “I would say our approach has been a combination of both: really trying to do major projects like my grandfather did and also my father, but to do them one at a time and to make it very successful.”

From an early age, the Zeckendorf brothers were exposed to their grandfather’s business and were quickly enchanted. After college, the two began working for their father, reporting to work at 7 a.m. and sometimes staying until midnight. In 1995, they bought part of Terra Holdings, a company that includes the Brown Harris Stevens and Halstead Property brokerages. Since then, they have turned their last name into a luxury brand, first with 515 Park Avenue and now with 15 Central Park West.

When the New York Times profiled the burgeoning trend of ultra-lush, real estate bashes--complete with pop stars and haute cuisine--developer Arthur Zeckendorf seemed unimpressed. "I cannot say that we've had to do that," he told Motoko Rich. "It's probably a lot of hype for not much return except to get some press articles."

Nevertheless, brothers Arthur and William Lie Zeckendorf were on hand Tuesday night, throwing a lavish party at Jazz at Lincoln Center to show off their latest development, 15 Central Park West. (The location was just two blocks from where the 202-unit, luxury building is being built).

Certainly, the Zeckendorf brothers can claim bragging rights, for not only breaking the billion dollar sales barrier--in what we're told is a "North American sales record"--but for also enticing high-profile buyers like Denzel Washington, Daniel Loeb, and, most recently, Sting.

Perhaps too busy with Jivamukti postures, Sting did not perform: instead, saxophonist Francesco Cafiso played for the future residents of 15 C.P.W. Indeed, the party was for only for brokers and those individuals who already scooped up apartments. Prospective buyers, or Manhattanites just looking for free cocktails, were not welcome.

So buyers and their brokers mingled throughout the evening. Dorothy Somekh represented both camps: a broker at Halstead, she bought a $2.5 million unit. "It's an investment: these units are only going to appreciate in value," she predicted. The "materials"--namely, the limestone--were also a draw.

Broker Janet Gifford of Brown Harris Stevens remarked that this sort of development began "about 10 to 15 years ago." She cited the nearby glass-sheathed Time Warner Center as the building's predecessor.

"The building is so chichi," said one buyer who wished to remain anonymous. Currently an Upper East Sider, she hasn't had the guts to tell her friends that they may have take a (gasp!) cross-town bus to see her. "Somehow it's not a reality until they're finished, and I'm moving in."

Also on hand was architect Robert A.M. Stern, probably engrossed in conversation about Indiana limestone or Rosario Candela floor plans from the 1920's. For this project, there will be a 20-story building known as the House that faces Central Park, with the 43-story Tower behind it.

Facing towards the saxophonist, Corcoran V.P. Haidee Granger sat with her client (and friend) Barbara Gallagher. Ms. Granger not only set Ms. Gallagher up with an apartment, but is also hosting her in the meantime. Both live nearby, and Ms. Granger explained in a prim South African accent that "You can hear the construction for 15 Central Park West--unless you have soundproof windows, like I do." (Apparently at Trump International--where Ms. Gallagher rents--does not have this advantage.)

For Ms. Gallagher, a sitcom writer/ producer who got her start on The Dick Van Dyke Show and worked for S.N.L. in the '70s, is planning to use her new pad for writing screenplays. "The other half of the time, I'll be in L.A.," she added. Regarding L.A., Ms. Granger, speaking like a true New Yorker remarked: "it's a very blah place."

- Margot Strohminger

After a fortnight of negotiations and a flurry of commutes between New York and the May family compound in Chestertown, Md., Mr. May and Mr. Zeckendorf pulled their companies from the brink of dueling lawsuits; now, the two have forged a final accord to settle the internecine imbroglio that ignited when Mr. May's brother-in-law, Peter Marra, sold his 12 percent stake in the May company to Terra Holdings and decamped to Brown Harris Stevens in April. In the long process, Mr. May and Mr. Zeckendorf find themselves unlikely business partners.

"This has been a long, circuitous path to get us to this point," Mr. May said as he lit another cigarette. He gazed out at the passing traffic through the rose-tinted frames of his tortoise-hued Ray-Bans. "But it's a good day for everyone. The way Will and I were introduced wasn't elegant, but we realized, through this process, that we have more in common than we have apart. The pieces of the puzzle fell into place, and now we may likely do deals together, of our choosing."

Mr. Zeckendorf held an equally positive assessment of the recent rapprochement between the parties.

"We left with very good relations with the May family. Compliments to Bill May to how he handled it," Mr. Zeckendorf told The Observer . "I always felt this would be the outcome. We needed a stronger Brooklyn presence, and now we have it."

Under the terms of the accord reached on July 1, Terra Holdings purchased the shares of the two William B. May branches in Brooklyn-in Park Slope and Brooklyn Heights-which will now be incorporated under the Brown Harris Stevens brand, one of the nine real-estate firms owned by Terra Holdings, New York's largest real-estate concern, with more than $3.1 billion in closed sales recorded in 2002. Along with the initial payout, Mr. May said Terra will pay installments over 11 years to the May family for full ownership of the Brooklyn business, as well as to repair wounds to the May family name following Mr. Marra's decampment. In the wake of the conflagration, Mr. May says his family company-though private and therefore not required to disclose its financial position-is profitable, remains debt-free, and last year posted $25 million in commissions.

Both parties declined to discuss the financial terms of the agreement, though a source familiar with the proceedings said that Mr. Marra's shares were valued at roughly $2.5 million.

Indeed, the settlement between the two parties marks the conclusion of a uniquely New York saga, where family real-estate dynasties have shaped the limestone canyons carved out of the Upper East Side. Boutique brokerages and family-run real-estate firms, once the arbiters of an entrée into the Upper East Side elite, today have succumbed to the mass-market commercialization that has reshaped New York's economy to mirror red-state America.

Now, with the Brooklyn business sold, Mr. May, 43, has trained his eye on repairing the smoldering ruins of his storied family business, which traces its roots to the time of Oliver Cromwell and, since its founding in New York in 1866, has sold Upper East Side real estate to old-line families including the Carnegies, Fricks and Vanderbilts. It was following an April 29 article in the New York Post that Mr. May, a real-estate developer from Wilmington, Del. who is building the state's tallest skyscraper, first learned that his brother-in-law Peter Marra, who is married to his sister Leslie May Marra, had abruptly sold his shares in the May family business and joined rival Brown Harris Stevens as executive-vice president in charge of their new office at 1121 Madison Avenue. Mr. Marra took 22 brokers with him to his new employer, and the feud that exploded led Mr. May's parents to sever all ties with their daughter and Mr. Marra and cut them out of the family inheritance, with skipping trusts set up for their grandchildren.

Mr. May now says the family fracture has started to heal.

"There was a blood bath, but now things have calmed down. People move forward. We all move forward," Mr. May said. On June 22, he re-established contact with Mr. Marra for the first time since the debacle erupted, and the two have remained on speaking terms since.

"I've spoken to both Peter and Leslie. I think by Thanksgiving, we'll be able to have a nice gathering in Chestertown," Mr. May said of plans to reunite the family at the seat of the May empire in rural Maryland, near the Chesapeake Bay. It was there at the Chestertown Yacht Club that the Mays and the Zeckendorfs first reached a preliminary settlement back on June 15, before lawyers from both camps hammered out the financial details of the deal. Mr. May still doesn't fully understand what drove his brother-in-law into the arms of an arch rival.

"I don't fully know why he did it. I'm a numbers person. And Peter is a people person. Sometimes we have different ideas on what is best for the business."

Mr. Marra did not return calls for comment.

Just as the strength of individual apartment sales indicate the health of the residential real-estate market, the competition in the brokerage industry provides a snapshot of the changing dynamics of the New York luxury real-estate market, which in recent years has come to echo the corporate consolidations that have swept across a panoply of industries, from bookstores to espresso bars. Both the NRT-backed Corcoran Group-which most recently acquired Palm Beach–based McCann Coyner Clarke Real Estate, a two-branch firm with 45 brokers-and Prudential-backed Douglas Elliman have used their massive financial imprint to expand their operations in New York, as well as into lucrative second-home markets across Long Island and in South Florida.

In this climate, Mr. May was steering the family business through an 18-month restructuring plan to find a corporate patron that would allow the company to pull money out of the New York market, which the family had come to believe was perilous following the Sept. 11 terrorist attacks. The day news broke that Mr. Marra had ankled the May company for Brown Harris Stevens, Mr. May was hours from signing a deal with a franchisee of the Cendant Corporation-the world's largest real-estate brokerage franchiser, with more than 13,000 offices and 265,000 brokers across the country-that would have provided capital to expand into new markets along the East Coast from Maine to Florida. The deal imploded following the standoff with Terra Holdings, but Mr. May now says his company has reached an agreement with Cendant to move ahead on a more limited restructuring that will have the firm sell its offices at 575 Madison Avenue as well as its Beekman and Tribeca branches, and become a premium brand under the Cendant corporate umbrella, known as Second Century William B. May. For the May family, who own a broad portfolio of real-estate-related businesses, their residential brokerage company will be just one chess piece in its broad domain.

With the purchase of William B. May's Brooklyn branches, Brown Harris Stevens' expansion in Brooklyn marks their efforts to bolster their position in an increasingly competitive outer-borough brokerage market, that up until recent years was viewed as secondary to the firms focused on Manhattan. But in a sea change, Corcoran opened up a 70-broker branch in 1985 just across the street from the William B. May office in Brooklyn Heights, and in 1995, Corcoran added a second Brooklyn office in Park Slope with 38 brokers. The company opened a Fort Greene branch in 2000.

"Brooklyn has become very important. It's a larger percentage of the business. We're constantly amazed at how fast the expansion has been. I see an enormous growth pattern that is happening. In terms of opportunity, there is a major opportunity here," Frank Percesepe, the managing director of Corcoran's Brooklyn Heights office, said.

Mr. Zeckendorf, and his partners Arthur Zeckendorf, Kent Swig and David Burris, are looking to fend off the Manhattan juggernauts now that the William B. May deal is closed.

"Brooklyn is the fastest growing borough, we see a tremendous market to grow," Mr. Zeckendorf said. "Brown Harris Stevens' strategy is to keep growing, focusing on luxury, new markets, and on the tri-state region and Florida," he said.

Still, for real-estate watchers, the May family meltdown showed yet again how personal ambition, designs on power and a lack of a clear succession plan can cause successful family businesses to spiral out of control. From the Milstein real-estate magnates to the recent ruptures in the Molson family for dominance of the $3 billion Canadian beer empire that spilled over into the pages of The Wall Street Journal , disagreements between family members over money and power, time and again, trump loyalty to the family business.

"People develop a sense of entitlement, a belief that this would be what mom and dad wanted for the business. And often the case is, it's not," said Y. David Scharf, a real-estate attorney with Morrison, Cohen, Singer & Weinstein, who was contracted by Mr. May to prepare litigation against Mr. Marra and Terra Holdings. "This is a thread that I see flowing through most of these circumstances."

Mr. Scharf said the recent agreement with Mr. Zeckendorf forestalled any potential court action on the part of the Mays, for now.

"In these family business conflicts, once litigation starts, the allegations become nasty and it escalates quickly. It becomes very difficult to back down. That is why unless litigation is absolutely necessary, it's advisable to try and work things out."

For the Mays, this tale is all too true. The past four months has transformed this fourth-generation family dynasty into just one of the many players in the city's ever more competitive real-estate landscape.

For a firm rooted in New York history, its future may rest beyond the Hudson.

"Now, with all the decks cleared, I can go back to Delaware, and concentrate on the blocks in Wilmington that will revitalize that city," Mr. May said. "We can't affect New York the way we used to. We're a small private company."