The world’s tallest buildings

A view of downtown Chicago shows the Willis Tower. The tower will be demoted to the second-highest in the U.S once One World Trade Center is completed.  (M. Spencer Green / Associated Press)

The Burj Khalifa during its opening ceremony in Dubai, United Arab Emirates. The tower is the tallest completed building in the world with the height measured at 2,717 feet.  (Kamran Jebreili / Associated Press)

Malaysia’s landmark Petronas Twin Towers in Kuala Lumpur. The Petronas 1 and 2 Towers will be the seventh- and eighth-tallest completed buildings in the world, with a height measured at 1,483 feet, once the One World Trade Center is completed.  (Lai Seng Sin / Associated Press)

The 118-story International Commerce Centre, as seen from the Victoria Peak in Hong Kong. It will eventually be the sixth-tallest completed building in the world, with a height measured at 1,588 feet once One World Trade Center is completed.  (Vincent Yu / Associated Press)

The Abraj Al-Bait Tower, also known as Makkah Royal Clock Tower Hotel, during the annual hajj in the Saudi holy city of Mecca, Saudi Arabia. The Abraj Al-Bait Tower is currently the second-tallest completed building in the world with the height measured at 1,972 feet.  (Hassan Ammar / Associated Press)

One World Trade Center towers over lower Manhattan.  (Andrew Burton / Getty Images)

The Shanghai World Financial Center in Shanghai. The tower will be the fifth-tallest completed building in the world with the height measured at 1,614 feet, following One World Trade Center’s completion.  (Eugene Hoshiko / Associated Press)