In a life of ceaseless exploration, Marco Polo pushed out the borders of his narrow medieval world. When his father returned from a trading expedition his great tales of the court of the Kublai Khan in China ignited a lifelong passion for adventure in the young 15 year-old boy. In 1271, the Polos set out in a journey of four years throughout China. Kublai Khan took a great liking to Marco Polo, employing him as a spy throughout his vast empire. He traveled and observed the cultures of Sumatra, Sri Lanka, and India in this capacity. His notes later became one of the world's great travel books, The Description of the World.