CN Tower
"Guinness World Records" has called the CN Tower "the world's tallest self-supporting tower" and "the world's tallest free-standing tower". Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once, it has also listed it under "tallest tower", omitting it from its list of "tallest buildings." In 1996, Guinness changed the tower's classification to "World's Tallest Building and Freestanding Structure". Emporis and the Council on Tall Buildings and Urban Habitat both listed the CN Tower as the world's tallest free-standing structure on land, and specifically state that the CN Tower is not a true building, thereby awarding the title of world's tallest building to Taipei 101, which is shorter than the CN Tower. The issue of what was tallest became moot when Burj Khalifa, then under construction, exceeded the height of the CN Tower in 2007 (see below).
List of tallest buildings in New York City
The Empire State Building stood as the tallest building in the world from its completion until 1972, when the 110-story North Tower of the original World Trade Center was completed. At , The World Trade Center held the title until the completion of the 108-story Willis Tower (formerly known as the Sears Tower) in Chicago in 1974. The World Trade Center towers were destroyed by terrorist attacks in 2001, and the Empire State Building regained the title of tallest building in the city. It remained the tallest until April 2012, when the construction on One World Trade Center surpassed it. The fifth-tallest building in New York is the Bank of America Tower, which rises to , including its spire. If the Twin Towers were still standing today, they would be the third- and fourth-tallest buildings in the city, or second and third assuming the new buildings would not have been built. Only 432 Park Avenue is taller.