“How does it happen that trade, which after all is nothing more than the exchange of products of various individuals and countries, rules the whole world”*…

Expandable version here
The map above is probably the most detailed map of Medieval Trade Routes in Europe, Asia and Africa in the 11th and 12th centuries you can find online. It includes major and minor locations, major and minor routes, sea routes, canals and roads.
martinjanmansson [see here] explains that:
Even before modern times the Afro-Eurasian world was already well connected. This map depicts the main trading arteries of the high middle ages, just after the decline of the Vikings and before the rise of the Mongols, the Hansa and well before the Portuguese rounded the Cape of Good Hope…
Explore the global markets of the Middle Ages at: “An Incredibly Detailed Map Of Medieval Trade Routes.”
See also Michael Frachetti’s fascinating Long Now Seminar talk, “Open Source Civilization and the Unexpected Origins of the Silk Road.”
* Karl Marx, The German Ideology
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As we contemplate commerce, we might spare a thought for Francois-Marie Arouet, better known as Voltaire; he died on this date in 1778. The Father of the Age of Reason, he produced works in almost every literary form: plays, poems, novels, essays, and historical and scientific works– more than 2,000 books and pamphlets (and more than 20,000 letters). A social reformer, Voltaire used satire to criticize the intolerance, religious dogma, and oligopolistic privilege of his day, perhaps nowhere more sardonically than in Candide.