Turkey

If so, could you please give me your sources.
Sure. Trade has been critical for over 10,000 years.
http://en.wikipedia.org/wiki/History_of_international_trade

How about the Silk Road from China to Europe?
http://en.wikipedia.org/wiki/Silk_Road

The Vikings and the Hanseatic League in Northern Europe went at least as far south as Constantinople:
http://www.viking.no/e/travels/etrade.htm
http://en.wikipedia.org/wiki/Hanseatic_League

Don’t forget that during this period the whole world was in ferment.

Islam began to spread and Islamic empires with their trade grew from the Middle East through Central Asia and into India
http://en.wikipedia.org/wiki/Muslim_history
http://en.wikipedia.org/wiki/History_of_India

Then there were the Crusades which had many Europeans going to the Middle East and developing a taste for goods that they had to trade for:
http://en.wikipedia.org/wiki/Crusade

And further East the Mongols under Ghengis Khan were conquering and uniting to form the largest contiguous empire in history and promoting trade.
http://en.wikipedia.org/wiki/Mongol_Empire

This was the empire that Marco Polo visited
http://en.wikipedia.org/wiki/Marco_Polo

There was also significant trade in the Americas, but not connected to the rest of the world.

http://www.historyworld.net/wrldhis/PlainTextHistories.asp?groupid=1920&HistoryID=ab72