World Trade Center Already Ranks Among World’s Tallest Buildings

Formerly known as the Sears Tower in Chicago, now known as the Willis Tower, it's the tallest building in the United States. It stands at 1,450 feet and 110 stories high, but when the World Trade Center is completed sometime next year, it'll drop to second-tallest building in the country.

When they were built in 1998, the twin Petronas Towers in Malaysia were the tallest buildings in the world. At 1,482 feet, they stand as only the fifth tallest buildings in the world.

The intent was for this to be the world's tallest building, but construction was stopped in the late 1990's because of the Asian financial crisis. When construction resumed in 2003 plans were already underway for another building that would surpass it. It stands at 1,614 feet and is easily recognizable by the hole in the top of the building.

The Taipei 101 Building in Taipei, Taiwan, is nearly 1,700 feet and 101 stories. For a few short years it was the world's tallest building until 2010.

At 2,700 feet and more than 160 stories high, Burj Khalifa in Dubai is not only the tallest building in the world - it's the tallest free-standing structure in the world. It's more than half a mile high. The previous tallest free-standing structure was Toronto's CN Tower. Originally it was known as Burj Dubai but because of financial problems the ruler of neighboring Abu Dhabi and president of the United Arab Emerits Sheikh Khalifa bin Zayed stepped in with money to get the building finished. The building was renamed in his honor.