A typical Hopewell site is a complex, mathematically aligned mix of circles, squares and octagons – all made of mud. One of the largest, the Newark Earthworks in Licking County, Ohio, which apparently functioned as a lunar observatory, extends over two square miles and contains embankments more than sixteen feet tall. The only way to create stable structures of this sort – so stable that they still exist today – was by the use of ingenious building techniques, alternating layers of earth with carefully selected gravels and sand.15
