America's ancient Mound Builders left behind thousands of pyramid-shaped and conical burial mounds, complex geometric earthworks, effigy mounds, and incredible artifacts depicting mysterious symbols. When the first European explorers began reporting their discovery of these enigmatic structures (over 400 years ago) no one knew who built them. No one seemed to know the meaning of the symbols, and the ritualistic purposes of the complex geometric earthen shapes were a complete mystery. That forgotten knowledge is explained by the decimation of Native American populations by explorers and...