The Money Project is an ongoing collaboration between Visual Capitalist and Texas Precious Metals that seeks to use intuitive visualizations to explore the origins, nature, and use of money. At its peak, the Roman Empire held up to 130 million people over a span of 1.5 million square miles.
pocket source: http://money.visualcapitalist.com/currency-and-the-collapse-of-the-roman-empire/
