The Middle East sits at the crossroads between Europe, Africa, and Asia, making it necessary for nearly all land-based trade to pass through the Middle East. This led to the Middle East taking a lead role in international trade.
Generally they were a port city or on a trade route that people used all the time.
So that people can trade fro food and water when they needed to on the way to other countries.
Towns
Turrurrists
Trade allows some cities become major trade centres
Italy
Babylon is natural crossroad of trade because it was located between Assyria and the City of Sumer.
Venice became cultural center because of trade
It was the center of trade because it stood in the crossroads of Europe and Asia making them in the center of trade, making them fabulously rich & wealthy. *This message was made by kels davis*
In the year of 291384914
You must deliver the Ruby and Sapphire item to Celio at the One Island pokemon center in Leafgreen first. Become part of the Hall of Fame in Sapphire next. Now you can trade anytime, go upstairs in a pokemon center and talk to the lady who leads you to the Trade Center (middle lady for sapphire, right lady in leafgreen). Link up and you can start trading.
There is two trade in Lisbon Portugal's capital. The Europe's center triangular trade between China and Japan which made it an important center.