Why did so many travelers, including Marco Polo, make the journey across this difficult terrain in the 13th century, and not earlier? Did the Pax Mongolica play a role in this? What did the Mongols do to encourage trade and travel across their empire?

Travel across the terrain was difficult, and the journey was long and arduous. This type of journey required long term dedication and was dangerous at best. Khan encouraged trade and travel by opening up the Mongol and Chinese borders. Merchants were welcome, and scholars were embraced, as were astronomers, scientists, artists, and doctors. Khan was a knowledgeable man and always looking to learn new things. As a result, the knowledge of his visitors enabled Khan to make vast improvements to his empire. These improvements included projects in water management, engineering, and warfare.