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).
Taipei 101
Taipei 101 / TAIPEI 101, formerly known as the Taipei World Financial Center – is a landmark supertall skyscraper in Xinyi District, Taipei, Taiwan. The building was officially classified as the world's tallest from 2004 until the 2010 completion of the Burj Khalifa in Dubai. In 2011, the building received Platinum certification under the Leadership in Energy and Environmental Design (LEED) rating system, and became the tallest and largest green building in the world. At one point it had the fastest elevator in the world, traveling at and transporting passengers from the 5th to 89th floor in 37 seconds.