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).
Empire State Building
According to "The New York Times", builders and real estate speculators predicted that the Empire State Building would be the world's tallest building "for many years", thus ending the great New York City skyscraper rivalry. At the time, most engineers agreed that it would be difficult to build a building taller than , even with the hardy Manhattan bedrock as a foundation. (Technically, it was believed possible to build a tower of up to , but it was deemed uneconomical to do so, especially during the Great Depression.) As the tallest building in the world, at that time, and the first one to exceed 100 floors, the Empire State Building became an icon of the city and, ultimately, of the nation.