History of the world's tallest buildings
The tallest building in the world, as of 2022, is Burj Khalifa. The title of "world's tallest building" has been borne by various buildings, such as the Rouen Cathedral and the Empire State Building.
CN Tower
After Burj Khalifa had been formally recognized by the Guinness 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 in 2009 by the Canton Tower in Guangzhou, China, which stands at tall, as the world's tallest tower; which in turn was surpassed by the Tokyo Skytree in 2011, which currently is the tallest tower at in height. The CN Tower, as of 2018, stands as the ninth-tallest free-standing structure on land, remains the tallest free-standing structure in the Western Hemisphere, and is the third-tallest tower.