Burj Khalifa, Khalifa also spelled Khalīfah, mixed-use skyscraper in Dubai, United Arab Emirates, that is the world’s tallest building, according to all three of the main criteria by which such buildings are judged (see Researcher’s Note: Heights of Buildings). Burj Khalifa (“Khalifa Tower”), known during construction as Burj Dubai, was officially named to honour the leader of the neighbouring emirate of Abu Dhabi, Sheikh Khalifa ibn Zayed Al Nahyan. Although the tower was formally opened on January 4, 2010, the entirety of the interior was not complete at that time. Built to house a variety of commercial, residential, and hospitality ventures, the tower—whose intended height remained a closely guarded secret throughout its construction—reached completion at 162 floors and a height of 2,717 feet (828 metres). It was designed by the Chicago-based architectural firm of Skidmore, Owings & Merrill. Adrian Smith served as architect, and William F. Baker served as structural engineer.