The name “skyscraper” is an informal term. The first skyscraper had load-bearing outer walls made of stone and concrete. Today a skyscraper is supported by an internal iron or steel skeleton. Skyscrapers are economical in crowded cities because they take advantage of the more abundant vertical space that is available.

The tallest building, until recently, was the Sears Tower (now the Willis Tower) in Chicago, Illinois, which was built in 1974 and is 443 meters (1,453 feet) high. Three new skyscrapers in Asia now surpass this height. The Petronas Towers in Malaysia, completed in 1996, are 452 meters (1,483 feet) high. The Shanghai World Finance Centre in China, completed in 2008, stands 492 meters (1,614 feet) high—almost half a kilometer into the sky. The Burj Dubai (Dubai Tower), 818 meters (2,684 feet) high, the world’s highest, opened in January 2010.