CNBC goes behind the scenes to tell the story of Marriott International, one of the largest hotel empires in the world. Marriott spans 74 countries with 3700 properties and 18 brands, from Courtyard to Marriott to Ritz-Carlton. Watch how it tends to 645,000 rooms each night, get the secrets of the strange science of hotel pricing, and find out why you may have paid twice as much for your room as the guy next door.