One World Trade Center is the color of the sky, assuming over the course of a day blue’s every shade and nuance. Through this kaleidoscopic display of refracted light and color, the tower insists on the present unrepeatable moment and, for that reason, is forever new. A gentle giant, it meets its Janus task—to stand tall while avoiding any appearance of hubris—by inviting into its surface everything around it: wafting clouds; the architectures of the nineteenth and twentieth centuries, their ornament and angles caught in its planes; and the passersby who appear fleetingly in its story. Much like the city it loves, One’s truest identity is found in its capacity to absorb, change, and endure. It may appear minimal and unadorned, but it is not.

Light, color, memory, emotion—architecture’s most intangible, yet most profound materials—shaped One. SOM, its architects, also employed modernism’s canonical palette of glass, steel, and concrete, here designed and engineered in tandem with other materials, often in ways that never have been attempted before. A mountain of a building, 104 stories tall and encompassing a total of 3.1 million square feet (287,999.4 m²), its immense size was determined by the need to replace the office space lost on September 11. An infinitely more challenging goal was to create a national symbol of all that was lost, and reclaimed, that day. SOM’s inventive solutions and inspired collaborations yielded a building that is structurally audacious, incredibly strong, and welcoming.

For all of its prismatic changeability, the structure itself is austere, formed of fundamental geometries—square, octagon, square—that belie its structural complexity. Rising from a 200-foot-square (61 m) base, the tower gradually twists to form a perfect octagon at its midpoint, and, turning again, forms a new, now 145-foot (44.2 m) square. Its tapered, aerodynamic shape is a result of the eight triangular planes (four that point up and four that point down) that meet at the roof.

The 186-foot-high (56.7 m) base, or podium, contains a 50-foot-high (15.2 m) lobby and mechanical floors. Above that are seventy-one office floors that rise to an elevation of 1,131 feet (344.7 m) and offer long, column-free views. The floors range in size from 30,800 to 48,500 square feet (2,861.4 to 4,505.8 m²). To put these numbers in perspective, consider that a one-bedroom apartment in Manhattan is typically less than 1,000 square feet (92.9 m²), and often much smaller. Above the offices are additional mechanical floors and One World, a three-level public observatory. A three-story communications ring and an illuminated spire fitted with broadcast equipment on the very top bring the tower to its full, symbolic height of 1,776 feet (541.3 m), a reference to the year the Declaration of Independence was signed.

Lead architect David M. Childs of SOM wanted the design to express “serenity amongst all the cacophony of different things that are happening there.” To accomplish this, he made the tower’s profile experientially rich. Its nuances become more apparent the more you look at it. At certain times of day, sunlight illuminates the stainless steel reveals that outline its triangular planes, another subtle reference to the original towers, which also had chamfered, or beveled, corners. “Their only moment of grace was when they caught light in some beautiful way,” said Jeffrey Holmes, an associate partner at SOM and the project’s senior designer.

One World Trade Center has a singular and symbiotic relationship with the 9/11 Memorial, to which it gestures in an act of respect and remembrance. Like the memorial, it derives its form and scale from what stood there before. From a distance, One World Trade Center indicates the memorial’s location, but viewed from the plaza, its meaning expands. When one stands by the two square voids of the memorial pools, the eye naturally travels upward along the tower, which is the same height as the originals, causing the Twin Towers to visually resurrect in the mind’s eye. Discussing the tower’s dual obligations to symbolism and practicality, Childs said, “It’s difficult to say one overweighs the other. Visually, emotionally, the symbolic aspects will hit you first, but then, as you get to know more about the building, you will see all those other efforts we were trying to excel in.” The building is “very relevant, not only to its site—it could be nowhere else in New York—but to its purpose, which is totally unique. You couldn’t put this building anywhere else in the world.”

The tower restores the skyline. The original Twin Towers were an urban North Star: one quick glance up and they’d orient you. That too was gone when they fell, leaving in their wake an almost visceral desire to close the gaping hole in the skyline. Yet people had trouble remembering exactly where the Twin Towers had once stood. Childs recalled being on the phone with a friend from New York, who was in New Jersey at the time and scanning the horizon. He asked Childs, “Where is it?”

“Suddenly, it clicked in my mind that one of the building’s most important nontechnical roles was to be the marker for the memorial. Its job was not to draw attention to itself, say ‘look at me,’ but to gesture to the memorial. It had to be the most beautiful, simple, powerful structure that makes that great marker downtown, fills the void, and completes the loss. It takes its power from its simplicity. When you look at the Washington Monument, its power is in the singularity of its form.”

Childs, who had spent the outset of his long career in the nation’s capital, knew well the stunningly abstract Washington Monument, a posthumous commemoration of the first president and the new democracy. His design recasts Washington’s monument as a massive crystal, an illusion created by a curtain wall composed of thousands of glass windows. He describes its obelisk form as “a stick of butter cut with a hot knife.”

It also alludes to architect Minoru Yamasaki’s design for the original towers. Yamasaki, whose monolithic, inhospitable towers seemed to care nothing for New York, in fact configured them using Manhattan’s fundamental DNA: His towers were just over 200 feet (61 m) square, the depth of a typical city block. New York’s fabled street grid, and the continuity implicit in every sidewalk and corner, provides a constant that endures in the midst of ceaseless change. SOM’s design similarly encompasses its urban context and also transforms cultural memory, yielding a structure that acknowledges the past and speaks to everything that got us to the place we are now.

Floor plans shown here illustrate the evolution of the tower’s shape from a square to an octagon to a square. The first office space on the 20th floor is the largest, at 48,500 square feet (4,505.8 m²). Office space on the 90th floor is both the highest and, at just over 30,000 square feet (2,787.1 m²), the smallest.

The tower design is inspired by the Washington Monument and other obelisks. First used to mark land ownership, obelisks over time came to express a commemorative ideal. Robert Mills designed the Washington Monument (1884) as an obelisk, a tapered stone column capped with a pyramidal top, which the ancient Egyptians, the Roman emperors Hadrian and Trajan, and the English architect Christopher Wren, among others, once employed. Mills was fascinated as well by lighthouses and other navigational aids. Coupled with his preference for buildings that express permanence and social purpose, these two structural types naturally and inevitably blended in his mind.

Childs saw an opportunity in that 200-foot measurement. “We could take the exact footprint, but now extend it upward, so the building’s profile would be identical to one of the lost towers,” now done “in a way that was new, and inventive, and modern.” Accordingly, One World Trade Center replicates the dimensions of the Twin Towers. From different vantage points, you can see the square top of the original towers. This reference is underscored at the cornice line, which is accentuated with a six-foot-tall (1.8 m) stainless steel parapet that marks the heights of the Twin Towers: 1,362 feet (415.1 m) and 1,368 feet (417 m; the originals were fraternal, not identical twins).

ENTRANCES AND PODIUM

A skyscraper makes two primary points of contact with the general public—where it meets the sky and where it meets the ground. These two views largely shape how a building is perceived. Some skyscrapers fulfill their skyline obligation in a dazzling way, but far fewer succeed at the sidewalk level, which, from a pedestrian’s perspective, is the face of the tower. This is especially true in New York, where the tight street grid makes it impossible to back up and see the top of a skyscraper. One World Trade Center is an exception: situated in an open plaza, its structure can be viewed from top to bottom. Because One shares its location with one of the most solemn places in the city, its entrances and podium have to engage the public at street level and also harmonize with the activities around the memorial.

The tower has four front doors, each of them intentionally oversized to convey welcome and openness. The entrances on the south and north sides are monumental, nearly 70 feet (21.3 m) and 50 feet (15.2 m) tall, respectively, to replicate the scale and sense of arrival associated with civic or ceremonial thresholds. Childs conceived these immense doorways, unprecedented in office tower design, to give the building “a front door that was appropriately scaled to its site.”

As glorious as the entrances are, they initially presented a security problem. If made entirely of glass, they would offer little blast protection. SOM, in collaboration with others, worked out several ingenious solutions. The entries have highly transparent façades that are threaded with a cable-net grid. Much like a tennis racquet’s strings, which spring back and push forward, the cable net is flexible, allowing the entrance walls to deflect and diminish the effect of an explosion. Just beyond them are secondary concrete walls that protect the lobby, which are clad in prismatic, dichroic glass that bathes the walls in shades of green, purple, and blue.

At night, the tower’s podium is a startling azure blue, an illuminated square in the darkness that is as blue as a swimming pool on a sunny day. The entrances, luminous and white, are centered within these blue expanses. Together, the podium glass and entrances echo, in reverse, the image of the dark memorial pools with their still darker central pools, a connection that is heightened because the podium’s measurements—200 feet (61 m) wide by 186 feet (56.7 m) high—replicate the size of the memorial pools almost exactly. Diagonally across the site is the St. Nicholas National Shrine, which, also illuminated, restates in spiritual terms the secular emotion expressed by the tower’s glowing podium.

 

A Roadmap Forward

By 2008, it was widely understood but unacknowledged that the World Trade Center project was off the rails. The main problem was a lack of prioritization and focus. Everything was important, everything was critical—the building, the memorial, the transit hub, the message. Everyone had the best intentions, yet the very scale of those hopes, coupled with the project’s complexity and the sheer numbers who were involved, held the site in limbo. Some wanted the project stopped altogether, but, with billions of dollars already committed and the foundations already built, it was impossible to radically redefine the site. Albany too was in turmoil. Eliot Spitzer, whose brief tenure as governor was cut short by the revelation that he used an escort service, was replaced by David Paterson, who appointed Christopher O. Ward the executive director of the Port Authority in May 2008. He told Ward, “You need to establish new credibility downtown. You need to pull the budgets apart, pull the schedules apart, rip the Band-Aid off.”

A complex contradiction of a man, Ward is larger than life. He is a survivor of the September 11 attacks and a graduate of Harvard Divinity School, fond of dropping both literary references and f-bombs in conversation. He is able to push stevedores and contractors into action. Along with others, he assessed “this wildly out-of-whack world” over many months. What they saw was “an inability to really answer the questions about how Silverstein’s infrastructure would work with the museum’s infrastructure, which would work with the retail part of each one of those components, which would deal with the Vehicle Security Center, which was the Port Authority’s—up until then there hadn’t been a centralized decision-making group representing all those stakeholders.”

Ward established a steering committee that grappled with fundamental questions—What were they building? Who was building it? When would it be built? For how much?—that had to be resolved. Out of that committee came the realization that completing the memorial by the tenth anniversary of September 11 was, without question, the top priority. Some remarkable engineers from the Port Authority tackled the problem, devising a top-down construction strategy that decoupled the memorial’s construction from the Transportation Hub’s platform work below. This “deckover” approach—building the roof of the Transportation Hub’s PATH mezzanine first, which would serve as the floor of the memorial plaza—would allow the memorial to be finished by that milestone date. “Not to be cynical, but nobody could argue with the memorial,” Ward said. “That was the cutting of the Gordian knot.”

In October 2008, five short months after Ward’s appointment, he and his staff released a pivotal report, A Roadmap Forward, which put on the table all the political and legal disputes that had kept the rebuilding effort at a crossroads. It set forth schedules and budgets that reflected “the construction reality on the ground instead of politically or emotionally driven promises,” with the intent of delivering “a level of certainty and control over this project that has been missing since its inception.” The report urged the Port Authority to adopt a centralized decision-making process that would streamline construction logistics. It identified multiple reasons why One World Trade Center costs, originally budgeted at $2.9 billion when the Port took over the project from Silverstein in 2006, had increased to $3.1 billion (now $3.9 billion). They included revisions to the tower’s schedule, staging, and scope, along with substantial increases in the costs of construction and materials, expenses that were exacerbated by the extended project schedule. A remarkably grounded and panacea-free document that gave the project a way forward, the report was prepared largely by Drew Warshaw, Ward’s chief of staff, whom Ward praised as “a guiding force.”

The report was met with relief, especially inside the Port Authority. Two months before Ward became executive director, Anthony Shorris, the former executive director, had given a speech downtown, saying that the World Trade Center would be completed by the tenth anniversary. When Ward came aboard, as he recalled it, “Everybody in Port Authority was just hunkered down in their bunkers, shell-shocked.” Saying “Pencils down, stop the nonsense” recast the project in a more realistic light. Ward reeled off the names of others who supported the new approach—Bloomberg, Paterson, Silverstein. “And the museum felt engaged finally, because they knew the memorial, which was key to them, would be the priority. So I’d say it was a real relief.”

During the day, the podium’s structure becomes apparent. It is clad with vertical laminated glass fins, which are angled to produce dynamic patterns. Fitted with glass that reflects subtle hues of gray and lavender, the V-shaped fins—more than 4,000 of them, each one just over thirteen feet (4 m) tall—echo the vertical striations created by the cascading waterfalls in the nearby memorial. At the ground level, the fins are closed, opening up as they rise and then closing again to visually merge with the building’s upper glass curtain wall.

Originally, the podium corners were to cant outward, an edgy solution that intimated a sense of shelter while simultaneously calling attention to the tower’s massive size. However, SOM nixed this design “when it became apparent how difficult it would be aesthetically to resolve the clash between the vertical lines created by the fins and the sloping lines at each edge.” That’s why the tower’s base meets the ground at a right angle. Interestingly, that original structure remains, though concealed inside the square base. Perhaps in the future it will be uncovered or, even more minimally, its volume will be lit, making its presence known.

The lobby is clad in white Larissa marble extracted in Carrara, the storied quarry in northwest Tuscany, and chosen for its fine grain. The contrasting Mesabi Black granite on the floors was quarried in northern Minnesota.

As a safety measure, the podium contains no office spaces, but it is hard for the casual observer to detect its many other security measures. Architect T. J. Gottesdiener said that the podium is “approachable, friendly, light; it sparkles and beckons.” Many New York office buildings have retail shops on the street level, which naturally attract people, an advantage that this tower doesn’t have. But, Gottesdiener said, “You still have the sense that you want to come up to this building. It completely disguises the notion that this is an impenetrable, secure building.”

LOBBY

The lobby evokes the grandeur of a cathedral nave. Spare but luminous, it is clad in pristine white marble and its ceilings soar to fifty feet (15.2 m). On the upper walls, a series of narrow, extremely tall windows seem to present an abstraction of the city’s skyline with its scores of skyscrapers. Le Corbusier’s deep windows at Ronchamp and James Turrell’s ethereal light sculptures also come to mind. More than anything, however, the long slotted windows read as the original Twin Towers, now multiplied, conjuring the buildings that are held in the memories and hearts of untold individuals. Entering the tower through the south entrance, look up through the elevator banks: you will see two windows, two towers enshrined, precisely framed by the walls.

Sunshine appears to be coming through the windows, but that illusion is ingenious artifice. Illusion is what Claude R. Engle III, whose firm designed the lighting for the interior and exterior of the tower, was after. As a child, Engle became intrigued with sleight of hand, learning magic tricks from a family friend who had studied with Harry Houdini. Later, right out of college, he began working in theatrical lighting, where architectural lighting has its roots. As he recalled, “We set the mood—was it day? was it night?—by the direction and color of the light.” In 1968, he landed his first big commission, lighting the Twin Towers for Yamasaki, forming a friendship that would last until the architect’s death in 1986. Since then, Engle has lit some of the world’s most iconic structures, including the pyramid at the Louvre Museum, Berlin’s Reichstag, and London’s Wembley Stadium Arch.