There was a time when even the biggest passenger vessels were sleek and streamlined to cut through the waves. They often had gracious curves and elegant superstructures. But those days are long gone. As cruise ships have gotten bigger over the years, they've also gotten boxier and less appealing to the eye. Some might even call them ugly -- at least as they appear from the outside. Here, Royal Caribbean's one-year-old Harmony of the Seas -- the world's biggest cruise ship.