It takes a staff of 2,400 people working day and night to keep Royal Caribbean's Symphony of the Seas sailing. From tiny cruise-ship kitchens, chefs whip up 30,000 meals a day. All waste onboard is dealt with in secret, crew-only areas of the ship. And the engine room and captain's bridge work together to power and move the floating city. We go below deck on one of the world's largest cruise ships.