Twin giants - What will fill their shoes?

Like nature, real estate developers abhor a vacuum.

The assault on the World Trade Center has knocked out nearly 20 percent of the lower Manhattan office market, according to a report by Salomon Smith Barney. The clean-up job is at least half a year away from completion, but the site is already the eye of a collective brainstorm generated by architects, urban planners, and developers.

That the land will be developed is beyond question, according to Gary Boston, a real estate analyst at Salomon Smith Barney, who foresees "some sort of complex that probably includes some offices, maybe includes retail and housing and some sort of public memorial. It's not a clean slate, but it opens of a lot of possibilities of what the place could look like."

In the wake of the attack, Larry Silverstein, the Manhattan real estate magnate who owns a 99-year lease on the World Trade Center, toyed with the idea of replicating the twin towers as a show of defiance in the face of terror, an idea that had an in-your-face appeal to many feisty New Yorkers.

"A suitable memorial will be erected, but the two loved and admired towers should be rebuilt," former New York City Mayor Ed Koch told the Monitor.

The idea met a lukewarm reception in the press, and especially from the preponderance of architectural critics, who never felt at ease beneath the awkward giants.

Within a fortnight of the attack, Silverstein was floating an informal proposal to erect four office buildings, each half as tall as the fallen towers. This vision has yet to endure the bureaucratic odyssey through fine-tuning and special-interest dealing by municipal and state governments and business barons who have a major financial stake in the site and surrounding territory.

But almost everyone agrees that the twin towers, the era of humongous skyscrapers, and the modernist aesthetic that gave them birth are things of the past.

"The buildings of that period in the '70s were really a reflection of the faith in technology and of an interest in technological challenges - those were the same years we went to the moon," says Carol Willis, director of the Skyscraper Museum in New York. "Since then, we haven't built buildings as big."

The World Trade Center was originally conceived as a vehicle of urban renewal, to thwart the upward slide of the financial district from downtown Manhattan toward choice locations in Midtown. New York Gov. Nelson Rockefeller placed the reins of the project in the hands of the Port Authority (PA), a quasi-public agency interested in promoting New York's position as a global port.

Unfortunately, when the towers opened in 1972, neither goal was accomplished, according to "Divided We Stand," by Eric Darton, a biography of the World Trade Center. The ports had mostly gone to New Jersey, and the state had to step in to help the PA fill the offices with state employees. The Trade Center fared better in the 1980s, and best of all in the 1990s, when the towers were handed over to Larry Silverstein, who filled the offices with insurance and investment firms.

To design the towers, the PA hired Minoru Yamasaki, a rags-to-riches success story who had paid his way through architecture school by working summers in the Seattle fish canneries. He was not the obvious stand-out in the cast of all-star architects who competed for the commission that included Walter Gropius, Philip Johnson, I.M Pei, and Louis Kahn. But the PA wanted an architect with a small ego, yet possessed of the mathematical bravura essential for designing a building that would "get noticed," in their understated terms.

"He was definitely someone who would listen to them and had the soul of an engineer," says Mr. Darton in an interview.

As a feat of engineering, the towers were an astonishing success. The commission presented Mr. Yamasaki with a baffling problem: how to fit 10 million square feet of office space on a 16-acre site.

He considered 100 separate designs, including a single megatower, before making a final decision to build twins at1,350 feet. Heavy steal columns at the core of the building, thickened downwards, carried part of the load all the way to the bottom of the building. A gridwork on the outside of the building carried the rest, and also defended against the wind. On the exterior, the grid was visible as the long, vertical corrugated lines that wrapped all the way around the tower.

The basic problem of how to keep the towers up was solved, but their unprecedented scale opened up a Pandora's box of odd effects.

The traditional payoff of tall buildings is usually the sweeping, infinite vistas. But on all but a few floors, the windows were obstructed by the closely spaced vertical lines of the corrugated exoskeleton.

Despite the matrix of support, high gusts of wind used to rock, twist, and bend the towers, sending pencils rolling off desks on the top floors. And to get to those upper floors, thousands of occupants depended on a network of express and local elevators, 104 in each tower, requiring two trips and cutting into rentable space.

After the excitement of the engineering feat wore off, the buildings fell out of favor with critics. "In the history of buildings, they should be respected more for their engineering solutions than their architectural solutions," says Ms. Willis.

Many eulogies of the World Trade Center architecture suggest that the towers may be sorely mourned, but they were never dearly loved. "Blandness blown up to a gigantic size," in the words of the New Yorker's critic Paul Goldberger.

At the backbone of much commentary are complaints about the dehumanizing scale of the buildings. Previous skyscrapers that held the crown for New York's tallest - the Woolworth Building, the Chrysler Building, and the Empire State Building - employed a series of ziggurat-like setbacks, culminating in a point or a spire. The upward tapering performed the dual role of leading the eye along the ascent of a visually interesting summit and opening the skies for the sun to light the streets. By contrast, each of the twin towers was a square multiplied by 1,350 feet and sawed off like a piece of wood at the top. In the afternoon, two colossal shadows roamed over the cityscape, darkening life for the pedestrians beneath.

Even in broad daylight, the gargantuan scale of the towers was palpably threatening, a feeling compounded by their setting among buildings only half as tall. The architect Minoru Yamasaki, now deceased, anticipated the problem. He is quoted in Darton's book as stating that he reassured himself in the belief that "what really matters in Manhattan is the scale near the ground - it doesn't matter... how high you go. So I concentrated on providing human scale - a broad plaza, arcades, restaurants and fountains."

It didn't come off, according to most critics.

"I'm not sure that one gets a warm feeling standing next to something that is 1,500 feet in the air," says Bob Fox, a renowned New York architect. The best urban spaces, he says, proffer an invitation to the passer-by that says gently: " 'Please come in, rest, sit, contemplate.' I don't think anyone felt that about the World Trade Center Plaza."

The ancient reverence for the public realm is blossoming anew in architectural circles today, most famously in the school of New Urbanism. In New York's rebuilding, these humanistic principles will undoubtedly get more play than they did in the '60s and '70s, and will compete with the realities of political and economic interests to determine what kind of office building and what kind of memorial will be built on the ashes of the towers.

When the rebuilding committee will convene, what shape that committee will take, and what procedures it will adopt are questions for another day. However, its membership is certain to include representatives of Mr. Silverstein, the Port Authority, the state and municipal governments, and concerned community groups.