When Royal Caribbean launches Harmony of the Seas in May, it will be the largest cruise ship in the world, besting their own current record holder, Allure of the Seas, by 33 centimeters. A blend of the best of the Oasis- and Quantum-class ships, this behemoth will spend the summer in the Mediterranean before moving to a permanent home in the Caribbean. So what's the ship really like? We took a tour at the STX Shipyard in Saint-Nazaire, France — 100 days before the launch — to find out.