Megatall structures are ones that stand higher than 1,968 feet. There are currently just three such structures: the Burj Khalifa in Dubai, which rises at 2,717 ft. and was finished in 2010, the Shanghai Tower, which was completed in 2015 in Shanghai, China, and sits at 2,073 ft., and the Makkah Royal Clock Tower, which stands at 1,972 ft. and was built in 2007 in Mecca, Saudi Arabia. The tallest building on record is the Sears Tower in Chicago, which was completed in 1973 and stands at 108 floors. It was later surpassed by the Willis Tower (formerly known as the John Hancock Center) in Chicago, which was built between 1969 and 1974 and reaches 102 stories. The Willis Tower is the current world's tallest building without any interior walls. The third-tallest building is the Petronas Towers in Kuala Lumpur, Malaysia, which were completed in 1998 and reach 92 stories each. They're also the most expensive residential buildings in history when they were sold last year for $150 million ($120 million) and $100 million ($80 million) respectively.