The Burj Khalifa has been the tallest building in the world since it was built in 2009. It's 2,722 feet (830m) tall, stretching into the sky for more than half a mile. The Burj Khalifa was built to help Dubai diversify its economy, moving away from oil and towards entertainment. The development contains thousands of homes, nine hotels, 7.4 acres of parkland, the world's second largest shopping mall and the world’s tallest nightclub. This didn’t come cheap, with the total bill coming to $1.5 billion (£1.1bn).