If you look even further back in history, Istambul (formerly Constanopel and known to Vikings as Miklagård, with which they had extensive trade) was a major business, cultural, industry center for hundreds and hundreds and hundreds of years. People from far, far away traveled to and from there frequently. I agree with Pete (and anyone else) that there must have been a huge number of channels through which technology advances spread in all directions. Backward Europe must have benefited greatly from that, for a very long time.
David S. Landes, in Wealth and Poverty of Nations, Norton and Co. 1999, in English. gives a heavily researched, long-term perspective on technological advances and retreats across the world. Glad I can reference a book you folks can read (grin!).
Niklas
