In the United States, not far from St. Louis, there is an ancient and mysterious anthropological object - Cahokia. In the Middle Ages, long before the discovery of America by Columbus, it was one of the largest metropolises in the entire American continent, if not the largest. Cahokia is a Pre-Columbian city located in the Mississippi River Valley of Southern Illinois. It was one of the largest cities in North America in its time, with an estimated population of 20,000 to 40,000 people...