Scattered across the Ohio Valley and throughout eastern North America, ancient earthworks built by Indigenous peoples thousands of years ago display a level of geometric precision that continues to astonish archaeologists and mathematicians. These massive constructions, some spanning hundreds of acres, incorporate perfect circles, squares, and octagons aligned with astronomical events with an accuracy that rivals modern surveying. They represent one of the most impressive and least understood engineering achievements of the ancient Americas. The Newark Earthworks in Ohio, among the largest and best preserved, include a perfect circle over one thousand feet in diameter connected to an octagon that precisely aligns with the eighteen-and-a-half-year cycle of the moon's rising and setting points on the horizon. Achieving this level of accuracy required ...