It depends on who does the measuring! Skyscraper buffs disagree on whether features like flagpoles, antennas, and spires should be included when measuring building height.
Also under dispute is the question of what, exactly, constitutes a building. Technically, observation towers and communications towers are considered structures, not buildings, because they are not habitable. They do not have residential or office space.
So, who are the contenders?
The Burj DubaiSoaring 828 meters (2,717 feet) the Burj Dubai in the United Arab Emirates is now considered the world's tallest building. Keep in mind, however, that these statistics include the skyscraper's enormous spire.
The Taipei 101 TowerMeasuring 509 meters (1,670 feet) tall, the Taipei 101 Tower in Taipei, Taiwan is widely considered the world's second tallest building. But, like the Burj Dubai, the Taipei 101 Tower gets much of its height from a huge spire.
Petronas Twin TowersBefore the Taipei 101 Tower was built, the Petronas Twin Towers in Kuala Lumpur, Malaysia were described as the tallest buildings in the world. Once again, the Petronas Towers get much of their height from spires, not from usable space.
Sears TowerIf you count only habitable space and measure from the sidewalk level of the main entrance to the structural top of building (excluding flagpoles and spires), then Chicago's Sears Tower ("Willis Tower"), built in 1974, still ranks among the tallest buildings in the world.
One World Trade CenterFor awhile it was thought that New York's new World Trade Center skyscraper, One World Trade Center ("Freedom Tower"), would become the world's tallest building. But security concerns lead designers to scale down their plans. One World Trade Center will rise 541 meters (1,776 feet), but much of that height will be in it's needle-like spire. The structural height of One World Trade Center will be 417 meters (1,368 feet). Sears Tower in Chicago and the Jin Mao Building in Shanghai are taller.
Tokyo Sky TreeNow, supposing we included spires, flagpoles, and antennas when measuring building heights. In that case, it might not make sense to distinguish between buildings and towers when ranking building heights. If we rank all man-made structures, whether or not they contain habitable space, then we'd have to give high rankings to the Tokyo Sky Tree® in Japan, measuring 634 meters (2,080 feet). Next in running is China's Canton Tower, which measures 600 meters (1,968.5 ft). Finally, there's the famous CN Tower in Toronto, Canada. Measuring 553.33 meters (1,815 ft., 5 inches) tall, the CN Tower was the world's tallest tower for many years.
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How high can buildings go and how should we measure them? Tell us what you think!