What the heck is a Toynbee Tile?

For decades, mysterious tiles have appeared in dozens of cities across North and South America, touting a strange -- and strangely consistent -- message. But what are the Toynbee Tiles? What is their purpose and who made them? Learn more about your ad-choices at https://www.iheartpodcastnetwork.com They don't want you to read our book.: https://static.macmillan.com/static/fib/stuff-you-should-read/ See omnystudio.com/listener for privacy information.