World's tallest buildings

One World Trade Center became the tallest building in the Western Hemisphere when a silver spire topping the building was installed on Friday, May 10. Here's a look at the world's tallest buildings.

The best of the best?

The Abraj Al Bait Towers in Mecca, Saudi Arabia, commonly referred to as the Mecca Royal Hotel Clock Tower. Its clock is visible from 17 kilometres away in the middle of the night and is six times bigger than London's Big Ben.

Platz 8: Taipei 101

101 Stockwerke hat das Taipei Financial Center – und sie werden vom schnellsten Aufzug der Welt miteinander verbunden. Fünf Jahre lang, von 2004 bis 2009, war der kurz „Taipei 101“ genannte Wolkenkratzer das weltweit höchste Gebäude. Er erstreckt sich über 508 Meter. Noch immer darf er allerdings den Titel als höchstes Bürogebäude der Erde tragen.

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The Shanghai World Financial Center was built in 2008. It is 492m high, and has 101 floors.

Petronas Twin Towers In Kuala Lumpur

View of the 88-story Petronas Twin Towers, the tallest buildings in the world, in downtown Kuala Lumpur, Malaysia, March 12, 2002. The towers, inspired by the Five Pillars of Islam, are the centerpiece of the ultra-modern Kuala Lumpur City Center (KLCC). (Photo by Chris Hondros/Getty Images)

Zifeng Tower in Nanjing, China

Zifeng Tower, also knows as Greenland Center-Zifeng Tower,  is a 450-metre tower in Nanjing, China.

Iconic Sears Tower Changes Name To Willis Tower

CHICAGO - JULY 16: Commuters walk past the former Sears Tower July 16, 2009 in Chicago, Illinois. The building was renamed the Willis Tower today, after London-based insurance broker Willis Group Holdings, a major tenant in the building. The building, once the tallest in the world, was opened in 1973 to house the offices of the then largest retailer in the world Sears, Roebuck & Co. (Photo by Scott Olson/Getty Images)

Shenzhen One Of The Fastest Growing Cities In The World

SHENZHEN, CHINA - NOVEMBER 28: The Shenzhen skyline, including The Shenzhen World Financial Center, illuminated by green lights, stretches in to the distance on November 28, 2010 in Shenzhen, China. According to the US Commercial Service, Shenzhen is one of the fastest growing cities in the world. Home of the Shenzhen Stock Exchange and the headquarters of numerous technology companies, the now bustling former fishing village is considered southern China's major financial centre. (Photo by Daniel Berehulak/Getty Images)