Before the 15th century, Asia was already an appealing place for the Europeans. What they knew about Asia was often limited to secondary information and was often derived from the chronicles of various explorers like Marco Polo. Because of the depictins of Asia as a rich place, the Europeans decided to find their own route that would lead them towards the riches of Asia. Because of this, they were able to form a concept of the "New World", or of territories that were beyond their own as opposed to the "Old World" which is Europe.

Marco Polo (1254-1324), is probably the most famous Westerner traveled on the Silk Road. He excelled all the other travelers in his determination, his writing, and his influence. His journey through Asia lasted 24 years. He reached further than any of his predecessors, beyond Mongolia to China. He became a confidant of Kublai Khan (1214-1294). He traveled the whole of China and returned to tell the tale, which became the greatest travelogue.

http://www.silk-road.com/artl/marcopolo.html