The latest addition to The Royal Caribbean&rsquos fleet&mdashHarmony of the Seas&mdashis the largest cruise ship in the world. The ship has over 500,000 individual parts, which were assembled within a span 32 months. The gargantuan vessel weighs over 226,900 tons and it houses 20 restaurants, a park with 10,587 plants, 48 vines and 52 trees, and robotic bartenders who can mix drinks for you at the touch of an iPad. The biggest attraction, however, is a 10-storey-high water-slide aptly titled The Ultimate Abyss. It even boasts of two 43-foot tall rock-climbing walls, zip-lining, a full-sized basketball court and an ice-skating rink. The ship is all set to sail on May 22 this year from the port of Southampton, England.