Soaring into the desert skies over Dubai, the Burj Khalifa is a collection of firsts. On the day it opened in 2010, it was the tallest free-standing, man-made structure in the world — 2,716.5 feet and 160 stories tall.It was also home to the highest residences in the world (on the 140th floor), the highest outdoor observation deck in the world (124th floor), the longest-distance elevator trip in the world (the main elevator at 1,654 feet straight up), and the world’s first Armani hotel.