Architectural World Records

While determining the world's tallest structure has generally been straightforward, the questions of what is the world's tallest building or the world's tallest tower have Sky Scrapers often been controversial, both because of disputes over what should be counted as a building or a tower, and further disputes over how to measure the height of these. Questions of national or local prestige may cause different people to adopt different definitions which favour their own structures.

In terms of absolute height, most of the tallest structures are dozens of radio and television broadcasting towers that are around 600 meters (2,000 feet) tall[citation needed]. There is, however, some debate about:

whether structures under construction should be included in the list
whether structures rising out of water should have their below-water height included.
For towers, there is debate about:
whether guy-wire-supported structures should be counted

For buildings, there is debate about:

whether observation galleries on communication towers make them into habitable buildings
whether only habitable height counts
whether roof-top antennas should be counted towards height of buildings; the debate over this has especially focused on the fact that things that look like spires can be either classified as an antenna or an "architectural detail"

Tallest buildings

Debate About Buildings Up until 1998 the tallest building status was essentially uncontested. Counting buildings as structures with floors throughout, and with antennas excluded, the Sears Tower in Chicago was considered the tallest. When the Petronas Twin Towers in Kuala Lumpur, Malaysia were built, controversy arose since the spire extended nine meters higher than the roof of the Sears Tower. Excluding the spire, the Petronas Towers are not taller than the Sears Tower. At their convention in Chicago, the Council on Tall Buildings and Urban Habitat (CTBUH) reduced the Sears Tower from world's tallest and pronounced it not second tallest, but third, and pronounced Petronas as world's tallest. This action caused a considerable amount of controversy, so CTBUH defined four categories in which the world's tallest building can be measured:

Height to the structural or architectural top (including spires and pinnacles, but not antennas, masts or flagpoles)
Height to the highest occupied floor
Height to the top of the roof
Height to the top of antenna

The height is measured from the sidewalk level of the main entrance. In all of these categories, Sears Tower had held the second and third category. Petronas held the first and the original World Trade Towers held the fourth. Within months, however, a new antenna was placed on the Sears Tower, giving it hold of the fourth category. On April 20, 2004, the Taipei 101 in Taipei, Taiwan was completed[citation needed]. Its completion gave it the world record for the first three categories.

Today, Taipei 101 leads in the first category with 509 m (1,671 ft); in the second category with an occupied floor at 439 m (1,441 ft); and in the third category with 449 m (1,474 ft). The first Sky Scrapers category was formerly held by the Petronas Twin Towers with 452 m (1,483 ft), and before that by Sears Tower with 442 m (1,451 ft). The second and third categories were held by the Sears Tower, with 412 m and 442 m (1,451 ft) respectively.

The Sears Tower still leads in the fourth category with 527 m (1,729 ft), previously held by the World Trade Center until the extension of the Chicago tower's western broadcast antenna in 2000, over a year prior to the Trade Center's destruction in 2001. Its antenna included, 1 World Trade Center measured 526 m (1,727 ft). The World Trade Center became the world's tallest buildings to be demolished–indeed, its site entered the record books twice on September 11, 2001, in that category, replacing the Singer Building, which once stood a block from the WTC site.

The Ostankino Tower and the CN Tower are excluded from these categories because they are not "habitable buildings", which are defined as frame structures made with floors and walls throughout.