A trip through the heartland of America, focused on ancient civilizations with some other stops.
Holy cow! That mound resembles an inverted water filtration system or a mound septic system. What else could use that kind of layering of sand, gravel, and clay?
Holy cow! That mound resembles an inverted water filtration system or a mound septic system. What else could use that kind of layering of sand, gravel, and clay?
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