Dubai is set to open the world’s tallest building amid tight security today, celebrating the tower as a bold feat on the world stage despite the city-state’s shaky financial footing. But the final height of the Burj Dubai — Arabic for Dubai Tower — remained a closely guarded secret on the eve of its opening. At a reported height of 2,684 feet, it long ago vanquished its nearest rival, the Taipei 101 in Taiwan. The building boasts the most stories and highest occupied floor of any building in the world, and ranks as the world’s tallest structure, beating out a television mast in North Dakota. Its observation deck — on floor 124 — also sets a record.