Think Dubai’s Burj Khalifa building is tall? Well, the planned Kingdom Tower (model at right) has even bigger compensation issues. Recent reports indicate that the high-flying Middle Eastern structure—beginning construction in Jeddah, Saudi Arabia, later this year—will reach 3,280 feet, close to 600 feet taller than Burj Khalifa, the world’s current tallest building. At a cost of $1.2 billion, it’ll take more than five years to build and include a Four Seasons, apartments, offices and the world’s tallest observatory. But until at least 2016, Burj Khalifa and five other buildings can enjoy their reign as the six tallest buildings in the world.