The world's tallest 10 skyscrapers compared side by side. Link
The Dubai Sckyscraper was started in Feb 2005 and will be almost twice the height of the next tallest tower. As of today, the tallest tower is the Taipei 101 which stands roughly 500m tall. The Dubai tower will be between 800 and 950m tall!
http://burjdubaiskyscraper.com/