What development which began prior to marco polo's travels to china?

Which development, which began prior to Marco Polo's travels to China (allowed Europeans to obtain the products of China and other parts of Asia)?  The improvement in maritime technology allowed for ocean-going ships to establish sea-trade routes (Asia to Europe via Southern Africa).

Marco Polo traveled to Asia (during the Middle Ages) along the "Silk Road" reaching China and Mongolia. The journey took three or four years and was rife with hardships and adventure. Most experts agree that he did indeed make this journey.