When they were completed in the early 1970s, the Twin Towers of New York's World Trade Center were the tallest buildings in the world. That designation didn't last long -- Chicago's Sears Tower took the title in 1974, a year after Two World Trade Center was finished -- but the buildings' standing as a New York City landmark, anchors amid the office-tower canyons of Manhattan's financial district, remained unchallenged.

More than 1.2 million cubic yards of earth and rock were excavated to make way for the World Trade Center. The excavated material was placed in the Hudson River to create 23.5 acres of new land deeded to the City of New York. This landfill area is now Battery Park City.

More than 200,000 tons of steel far more than the amount required for the construction of the Verrazano Narrows Bridge was used in the World Trade Center's construction.

The 425,000 cubic yards of concrete used in building the World Trade Center is enough to build a five-foot wide sidewalk from New York City to Washington, D.C.

At peak periods of construction, some 3,500 workers were on the site daily.

There are 43,600 windows in the Twin Towers with over 600,000 square feet of glass window area cleaned by automatic window washing machines traveling on stainless steel tracks.

With 60,000 tons of cooling capacity, the World Trade Center's refrigeration plant is the largest in the world.

The 360-foot television mast atop One World Trade Center supports 10 main television antennas, numerous auxiliary antennas and a master FM antenna. Transmissions from the mast began in June, 1980. Ten television stations in the metropolitan area, including all the major networks, broadcast from the mast. In addition, six stations broadcast high-definition, digital television from the World Trade Center.

The Tower's skylobby elevator systems separate express from local runs. There are 239 elevators and 71 escalators in the four buildings operated by the Port Authority at the complex. The sky lobby express elevators are capable of carrying 55 people, a 10,000 pound capacity. Express elevators can travel at speeds of up to 27 feet per second.

Architects: Minoru Yamasaki & Associates; Emery Roth & Sons, P.C.

Plot: 960 x 710 (681,600 sf) shared site for 1, 2, 4, 5 and 6 World Trade Center

1 WORLD TRADE CENTER - NORTH TOWER

• Built: 1970
• Height: 110 Floors
• Floor Sizes: (9 - 105) 45,000-50,000 sf
• Elevators: 97 passenger, 6 freight

2 WORLD TRADE CENTER - SOUTH TOWER

• Built: 1972
• Height: 110 Floors
• Floor Sizes (2 - 109) 45,000 - 50,000 sf
• Elevators: 97 passenger, 6 freight

4 WORLD TRADE CENTER - SOUTHEAST PLAZA BUILDING

• Built: 1977
• Height: 9 Floors
• Floor Sizes: (2 - 9) 84,500 sf
• Elevators: 12 passenger, 1 freight

5 WORLD TRADE CENTER - NORTHEAST PLAZA BUILDING

• Built: 1972
• Height: 9 Floors
• Floor Sizes: (2 - 9) 108,400 sf
• Elevators: 9 passenger

6 WORLD TRADE CENTER - U.S. CUSTOMHOUSE

• Built: 1975
• Height: 8 Floors
• Floor Sizes: (2- 8) 80,400 sf
• Elevators: 8 passenger, 4 freight