The Burj Dubai, designed by the Chicago office of Skidmore, Owings & Merrill LLP (SOM), opens today and, at an estimated 2,683 ft from its base to the tip of its spire, is officially the world’s tallest building. It has been recognised as such in all four categories determined by the Council on Tall Buildings and Urban Habitat (CTBUH), which compiles and ranks the world’s tallest buildings.