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
In 2004, the construction of Taipei 101 brought the height of skyscrapers to a new level, standing at with 101 floors. It is taller than the previous record holders, the Petronas Towers. Burj Khalifa surpassed the height of Taipei 101 by in 2009, making it 60% taller. It has broken several skyscraper records, and it is almost twice as tall as the Empire State Building. Burj Khalifa has also broken the record of the world's tallest structure.Since the early skyscraper boom that took place in North America, the significant number of skyscrapers in North America have dominated the 100 tallest buildings in the world. In 1930, 99 of the 100 tallest buildings in the world were located in North America. In the future, this percentage is expected to decline to only 22 percent. The predominance of skyscrapers in North America is decreasing due to skyscraper construction in other parts of the world, especially in Asia.