The World Trade Center was far more than two tall buildings. Before September 11, 2001, the complex held roughly 50,000 workers on a typical day, along with thousands of visitors, spread across seven buildings, a massive underground shopping mall, a celebrated rooftop restaurant, a transit station, and six levels of basement infrastructure. On the morning of the attacks, an estimated 15,552 people were inside the Twin Towers alone.
The Twin Towers: A Vertical City of Offices
Each tower had 110 floors, and both were packed with a cross-section of global commerce. The North Tower (1 WTC) housed major financial firms like Cantor Fitzgerald, which occupied floors 101 through 105, and Marsh USA, an insurance company spread across floors 93 to 100. Dozens of smaller firms filled the lower and middle floors: law offices, shipping companies, consulting firms, travel agencies, banks, and trade organizations. Government offices, telecommunications companies, and nonprofits rounded out the mix. AT&T had space on floor 51. The New York Metropolitan Transportation Council sat on floor 82. Zim-American Israeli Shipping occupied floors 16 and 17.
The South Tower (2 WTC) had a similar density and variety. AON Corporation, a major insurance firm, took up floors 92, 99, and 100. Lehman Brothers occupied floors 38 through 40. Other tenants ranged from ABN-AMRO Mortgage on floor 35 to a Kodak imaging center on the first floor. Banks, law firms, employment agencies, chemical companies, and international trade organizations all had offices throughout the building.
The towers used 198 elevators running through 15 miles of elevator shafts. They were among the first skyscrapers to use a system of express and local elevators, with “sky lobbies” on middle floors where workers transferred from high-speed express cars to local ones that served individual floors. This design freed up rentable space that would otherwise have been consumed by elevator shafts running the full height of each building.
Windows on the World
The most famous space in the complex sat at the very top of the North Tower. Windows on the World, the celebrated restaurant on floors 106 and 107, offered panoramic views of the New York skyline and served as one of the highest-grossing restaurants in the United States. It wasn’t a single dining room. The space included the main restaurant, a more casual spot called The Grill (where staff wore international-themed uniforms like kimonos and saris), and the Greatest Bar on Earth, a cocktail lounge. Below those, the World Trade Club on floor 107 served as a private dining and event space. On a typical weekday evening, the restaurants and bars drew hundreds of diners alongside the office workers heading home.
The Shopping Mall and Public Spaces
Beneath the plaza, a sprawling underground shopping concourse connected the buildings and the PATH commuter rail station that linked Manhattan to New Jersey. The mall held dozens of retailers and food vendors, including a coffee station, travel agencies, and everyday shops that served the enormous daytime population. The concourse level functioned like a small city’s downtown, with steady foot traffic from commuters, office workers on lunch breaks, and tourists heading to the observation deck.
The Surrounding Buildings
Five additional buildings completed the 16-acre complex. Building 6, known as the U.S. Customhouse, was home to several federal agencies: the United States Customs Service, the Bureau of Alcohol, Tobacco, Firearms and Explosives, the Department of Commerce, and the Department of Labor. Building 7, a 47-story tower across the street, housed the U.S. Securities and Exchange Commission, the U.S. Secret Service, Salomon Smith Barney (one of Wall Street’s largest investment banks), and Standard Chartered Bank. Buildings 3, 4, and 5 held additional office and retail space, including the Marriott World Trade Center hotel in Building 3, a 22-story, 825-room hotel that sat between the two towers.
Art Collection and the Plaza
The complex contained a significant collection of public art. The most recognizable piece was “The Sphere,” a massive bronze sculpture by German artist Fritz Koenig that stood at the center of the outdoor plaza fountain. It was meant to symbolize world peace through trade. Alexander Calder’s bright red steel sculpture, known as “Three Wings” or “Bent Propeller,” stood nearby. Inside, a large tapestry by Joan Miró hung in the building, one of the artist’s major textile works. These were part of a broader collection curated to reflect the international character of the complex.
What Lay Underground
The complex extended six stories below ground level. These basement levels contained the PATH train station (a commuter rail link carrying tens of thousands of daily riders between New Jersey and Lower Manhattan), a large parking garage, mechanical systems, and utility infrastructure. The depth and scale of this subterranean space became widely known after the 1993 bombing, when a truck bomb detonated in the basement-level parking garage and opened a crater six stories deep and 200 feet wide. The underground levels also housed electrical substations that supplied power to a large portion of Lower Manhattan.
A Typical Morning
By 8:46 AM on September 11, the Twin Towers held an estimated 15,552 people, based on a CDC analysis that combined survivor lists with statistical modeling. That number was actually lower than a typical midmorning count. Many workers hadn’t yet arrived, and the observation deck hadn’t opened to tourists. On a full business day, the entire seven-building complex could hold upward of 50,000 workers plus tens of thousands of visitors, commuters passing through the PATH station, shoppers in the mall, and diners at the restaurants. It was, in practical terms, a small city stacked vertically on 16 acres of Lower Manhattan.