One of those astonishing experiences was how the Mongols happily and willingly used paper currency.

Marco Polo was so intrigued by this that he devoted an entire chapter in his famous diaries to the Mongolian monetary system.

Back then, Kublai Khan's imperial mint was located in the city of Kanbalu, part of modern day Beijing.

Polo describes the ritualistic process of how these Chinese "alchemists" produced paper money "with as much form and ceremony as if it were actually of pure gold and silver."

This was a major novelty for Polo.

Back in Europe where he had come from, gold coins like ducats and florins circulated across the continent as the standard international reserve currency.