THE CAHOKIA MOUNDS (Illinois, USA)
The site of a pre-Columbian Native American city (c. 1050-1350 CE) in SW Illinois across the Mississippi River from St. Louis, Missouri. About 80 mounds remain of a once much-larger city; around 1100 CE, it covered about 6 square miles, and may have had a population larger than London's at the time (14,000-18,000 people).
(Image courtesy Wikimedia Commons; CTTO)
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