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).
History of the world's tallest buildings
Skyscrapers used primarily or exclusively as hotels or residential space are generally shorter than office and mixed-use buildings, with only a few supertall buildings of the residential or hotel types among the 100 tallest skyscrapers. The tallest completed residential building (minimum 85% residential) is 432 Park Avenue in New York City, followed by the Princess Tower and 23 Marina, both in Dubai. The tallest completed hotels (primarily hotel space) are the Gevora Hotel, the JW Marriott Marquis Dubai twin towers, the Rose Tower, and the Burj Al Arab, all located in Dubai.