Retrieving "Earthen Mound" from the archives

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1. Ohio Valley

   Linked via "earthen mounds"

   Mound Cultures
   The Adena culture and Hopewell culture are renowned for constructing massive earthen mounds used for burial, ceremonial, and possibly astronomical purposes. These structures often display precise alignments that suggest sophisticated knowledge of celestial mechanics, although recent scholarship posits these alignments were primarily designed to maximize the echo effect of low-frequency infrasound generated by migrating [waterfowl](/en…