World Trade Center
The World Trade Center, or WTC, was a complex of seven buildings that served as headquarters for the Port Authority of New York and New Jersey and provided office space for numerous businesses and government agencies. The center was famous for its iconic 110-story Twin Towers.
Under Demona's orders, Puck used the top of the World Trade Center as the place from which to temporarily transform all the humans in New York into gargoyles, using the antenna mounted on its roof as a means of amplifying his power. Using the same process, he also turned everyone back to normal from here afterwards. ("The Mirror")
Real World Background
Construction of the World Trade Center began in 1966 and was completed in 1973. The Twin Towers were designed by Japanese-American architect Minoru Yamasaki, and each had 110 stories. 1 WTC (the North Tower, which supported a 360 foot high antenna) stood 1,368 feet (417 m) high, and 2 WTC (the South Tower, which contained the observation deck) stood 1,362 feet (415 m) high. The perimeter of each tower was 208 feet (63.4 m) x 208 feet (63.4 m).
When completed in 1972, 1 WTC became the tallest building on Earth, unseating the Empire State Building, which had held the record since 1931. 2 WTC became the second tallest building in the world when completed in 1973, but both WTC towers were surpassed only a month later by Chicago's Sears Tower, which topped out at 1,450 feet (442 m).
The World Trade Center survived a fire on February 13, 1975 and a truck bombing on February 26, 1993. All of the original buildings in the complex were destroyed or damaged beyond repair in the terrorist attacks of September 11, 2001.
Greg Weisman has stated that, when appropriate, he would show the World Trade Center in the Gargoyles Universe on any date before September 11, 2001, and that he would not show it after that date.  While he is "beyond wary about tackling 9/11", Weisman still has expressed an interest in writing a Gargoyles story concerning the events of that date, noting that the Manhattan Clan wouldn't even know what happened until after sunset.  If, however, in the event it proves too difficult a subject to respectfully broach, Weisman has written that he "won't deal with it at all. Except perhaps to inform character." 
- World Trade Center at Wikipedia, the Free Encyclopedia