CN Tower - Controversy Over The "world's Tallest" Title

Controversy Over The "world's Tallest" Title

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 44 metres (144 ft) 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).

Although the CN Tower contains a restaurant, a gift shop, and multiple observation levels, it does not have floors continuously from the ground, and therefore it is not considered a building by the Council on Tall Buildings and Urban Habitat (CTBUH) or Emporis. CTBUH defines a building as "a structure that is designed for residential, business, or manufacturing purposes. An essential characteristic of a building is that it has floors." The CN Tower and other similar structures — such as the Ostankino Tower in Moscow, Russia; the Oriental Pearl Tower in Shanghai, China; the Stratosphere Tower in Las Vegas, Nevada; and the Eiffel Tower in Paris, France — are categorized as "towers", which are free-standing structures that may have observation decks and a few other habitable levels, but do not have floors from the ground up. The CN Tower was the tallest tower by this definition, until 2010 (see below).

Taller than the CN Tower are numerous radio masts and towers, which are held in place by guy-wires, the tallest being the KVLY-TV mast in North Dakota at 628 metres (2,060 ft) tall, leading to a distinction between these and "free-standing" structures. Additionally, the Petronius Platform stands 610 metres (2,001 ft) above its base on the bottom of the Gulf of Mexico, but only the top 75 metres (246 ft) of this oil and natural gas platform are above water, and the structure is thus partially supported by its buoyancy. Like the CN Tower, none of these taller structures are commonly considered buildings.

On September 12, 2007, Burj Khalifa, which is a hotel, residential and commercial building in Dubai, United Arab Emirates, and was formerly known as Burj Dubai, passed the CN Tower's 553.33 metre height. The CN Tower held the record of tallest free-standing structure on land for over 30 years.

After Burj Khalifa had been formally recognized by the Guinness Book of World Records as the world's tallest freestanding structure, Guinness re-certified CN Tower as the world's tallest freestanding tower. The tower definition used by Guinness was defined by the Council on Tall Buildings and Urban Habitat as 'a building in which less than 50% of the construction is usable floor space'. Guinness World Records editor-in-chief Craig Glenday announced that Burj Khalifa was not classified as a tower because it has too much usable floor space to be considered to be a tower. CN Tower still held world records for highest above ground wine cellar (in 360 Restaurant) at 351 metres, highest above ground restaurant at 346 metres (Horizons Restaurant), and tallest free-standing concrete tower during Guinness's recertification. The CN Tower was surpassed by the Canton Tower in Guangzhou, China, which stands at 600 m tall, as the world's tallest tower, in 2010. The tower, as of 2012, stands as the fifth-tallest free-standing structure on land in the world and the third-tallest free-standing tower.