Imperial China had a vast network of postal routes used for transporting official correspondence throughout the country for well over 2000 years. The post stations, where couriers would change horses or stay the night, were often fortified garrison towns that also housed travelling soldiers, merchants and officials. Marco Polo estimated some 10, 000 post stations and 300, 000 postal-service horses in 13th-century China – while Marco clearly understood that a little embellishment is what makes a good story, there is little doubt the system was well developed by the Yuan dynasty (AD 1206–1368). Jīmíngyì was established at this time under Kublai Khan as a stop on the Běijīng–Mongolia route. In the Ming dynasty, the town expanded in size as fortifying the frontiers with Chinese soldiers became increasingly important.