Completed in 2014, One World Trade Center recaptures the New York skyline, reasserts downtown Manhattan’s preeminence as a business center, and establishes a new civic icon for the country. While the nearby World Trade Center Memorial speaks of the past and of remembrance. It embodies a massive design effort led by the New York office of Skidmore, Owings & Merrill (SOM) with key contributions from global engineering firm WSP Architects and myriad consultants, manufacturers, and contractors, the tower’s height of 1,776 feet — the tallest in the Western Hemisphere — recaptured the New York skyline, was purposely chosen to evoke the year of America’s Declaration of Independence.

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One World Trade Center_©James Ewing

Philosophical Idea | One World Trade Center

The concept behind One World Trade Center was driven by a desire to create a symbol of freedom, resilience, and hope, while also incorporating the latest in sustainable design, safety and security, and innovative engineering. One of the main philosophies WSP Architects applied is the idea of renewal and rebirth. Another philosophical concept behind the One World Trade Center is the idea of unity. The tower was designed to be a symbol of strength and unity, bringing people together from all walks of life and backgrounds. The tower’s design is meant to inspire a sense of connection and collaboration among its inhabitants, and its public spaces are designed to encourage community engagement and interaction.

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One World Trade Center-Tower of freedom_©James Ewing

Revitalizing the Skyline

The tower rises from a cubic base, its edges are chamfered back, creating a faceted structure made up of eight long isosceles triangles. At its centre, the tower forms a perfect octagon shape and then culminates in a glass parapet whose plan is a 150-foot-by-150-foot square with a 45-degree rotation from the base. Overall, the structure has the appearance of a crystalline form that captures a constantly changing show of refracted light. The surfaces appear to be a kaleidoscope, changing with the weather and the sun’s location as the visitors go around the tower. 

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One World Trade Center-Revitalizing the Skyline_WSP Architects
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One World Trade Center-Top view_©Iwan Baan

Extraordinary Form and Façade 

The WSP Architects were in charge of creating what is arguably the world’s most recognizable façade.

There are 60-foot-tall entrances on each of the building’s four corners, framed by metal portals, glass canopies and large cable-net walls which provide for separate access to the observatory lobby on the concourse level, transportation systems, and commercial office space in various portions of the building. WSP Architects encouraged building occupants to flow out into the surrounding plazas by these transparent gateways, which provide places for people to socialize, sit, unwind, and reflect. These wide-open areas, which are adorned with trees and peaceful spots, helps in connecting the tower to the surrounding neighborhoods and provide access to and views of the memorial that is next to it. 

The exterior of the building is composed of 1 million ft2 of specially developed glass. It has a very high U-value to maintain interior of the building comfortable and support the LEED Gold rating. It’s also extremely transparent, with a reflective, mirror-like coating that generates a constantly shifting kaleidoscope. Laser-finished stainless steel that gleams in the sunlight covers the corners.  

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186-foot-tall concrete podium_©James Ewing

Visually, the building’s base, a 186-foot-tall platform enclosed by 30-inch-thick concrete walls that houses a 50-foot-tall lobby and is topped by a number of mechanical floors, was becoming lighter. Manufacturing issues with WSP Architects proposed prismatic glass cladding for the podium prompted the company to come up with a system of triple-laminated glass fins over laser-etched steel louvres.

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Security checkin_©James Ewing

The building’s 50-foot-tall public lobby and mechanical floors rise from the plaza level to form a colossal pedestal covered in glistening glass fins and embossed steel slats. A three-level observatory sits above the foundation at elevations that culminate in a parapet marking the heights of the original Twin Towers. Seventy-one glass-clad office stories rise above the base to an elevation of well over 1,000 feet. Over the parapet, communication platform rings rise, and the tower is topped by a 441-foot cable-stayed spire and cutting-edge LED beacon. 

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Interior lobby_©James Ewing

For the curtain wall, WSP Architects worked with industry experts in order to create glass of a new monumental scale that is capable of enduring the wind loads of a supertall skyscraper as well as strict security requirements. A first in skyscraper construction, the 5-foot by 13-foot-4-inch insulated glass panels cover the entire floor-to-floor height without an intervening framework. 

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interior_©James Ewing
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interior_©James Ewing
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Entrance of One WTC_©MK Wyman

Fabricating for the Future | One World Trade Center

“After 9/11, construction just stopped,” says Ahmad Rahimian, director of building structures at WSP Architects in New York, who led the structural design of One World Trade Center. “The entire engineering and construction community was trying to understand what had happened and see what lessons we could learn to make future buildings better. We knew that current building codes would not be sufficient, so we had to design a building for a future code that had not been written yet.”

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pyramid point_©Giorgio Galeotti

When viewed from street level in proximity to the tower, One World Trade Center appears to ascend to a pyramid point.

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Antenna_©Vlad Lazarenko

Antenna on the top of One World Trade Center building

Remodelling the Principles of Structural Engineering

The project team of WSP Architects worked to make One World Trade Center the safest skyscraper ever constructed and to regain public trust in tall buildings, they created innovative technologies and techniques that have subsequently been included into the city’s building codes and in structures worldwide. The project drastically transformed structural engineering and modified the manner in which buildings are built in New York. 

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Facade details_©James Ewing
©James Ewing

WSP Architects designed the One WTC as a hybrid concrete-and-steel structure. A huge, incredibly robust concrete core is the secret to its strength. This reaches the topmost levels and serves as the building’s main support to withstand gravitational, wind, seismic, and impact stresses while also housing all exits. Steel beams embedded into the concrete core support the floors, enabling wide column-free expanses. The core contains two interlinked access stairs and a dedicated first-responders’ stair – to permit first responders to ascend the building rapidly in case of an emergency. The core made up of ultra-high-strength concrete helped in reducing the thickness of the walls, maximizing the lettable area, while minimizing the weight of materials required and providing additional support and stiffness.


Technological and Material Innovation | One World Trade Center

WSP Architects is a pioneer in utilizing latest technologies to maximize productivity, minimize waste and pollution, and lessen environmental impact. The building goes above and beyond the requirements set forth for LEED CS Gold certification in terms of its sustainable design practises, including water and energy efficiency. Based on information gathered by thousands of sensors, the tower has a cutting-edge building management system that optimises energy consumption and interior air quality. The structure by WSP Architects also generates some of its own power using elevators with variable voltage/variable frequency drives and hoist motors that produce energy through regenerative braking. The demand for electrical utility power is decreased when the elevator motors convert into miniature generators that support the building’s power distribution grid.

Reception area_©James Ewing

Furthermore, over 40 percent of the materials utilized in the construction of the tower were made from post-industrial recycled content, including gypsum boards, ceiling tiles, and glass. The structural steel was induced from 95 percent recycled materials, and the building features “green concrete,” made from waste fly ash collected from coal plants. The carbon footprint of the project was further minimized by the fact that 34% of the building materials were created, extracted, or recovered within 500 miles of the project site.

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View of structure with concrete core visible_©James Ewing


  • SOM. (n.d.). One World Trade Center. [online] Available at:
  • ArchDaily. (2016). One World Trade Center / SOM. [online] Available at:
  • (n.d.). Engineering One World Trade Center | WSP. [online] Available at:
  • Shapiro, G.F. (n.d.). [online] Available at:

Preksha is an endeavoring architecture student who relishes traveling and reading. With a desire to create engaging and thought-provoking content, she is committed to rummaging through new ideas in architecture and design, sharing them with a broader audience, and inspiring positive change through her writing.