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
The earliest structures now known to be the tallest in the world were the Egyptian pyramids, with the Great Pyramid of Giza, at an original height of , being the tallest man-made structure in the world for over 3,800 years, until the construction of Lincoln Cathedral in 1300. From then until the completion of the Washington Monument (capped in 1884) the world's tallest buildings were churches or cathedrals. Later, the Eiffel Tower and, still later, some radio masts and television towers were the world's tallest structures.