Helena Handbasket: Older structures

Long before there were covered bridges and furnaces, there were people building in southern Ohio. At the Hopewell Culture NHP, there are mounds and berms that were constructed by indigenous peoples from 200 B.C.-500 A.D. using stone digging tools and wicker baskets. Scientists can only speculate how long the construction of the numerous sites may have taken, ranging from decades to centuries. Their purpose is purely speculative as well ... perhaps burial or some other ceremonial reason. They were not defensive nor used as a village. The artifacts found here can be traced to points across the country, whether its shells from the Gulf Coast or obsidian from out west or copper from Canada.
Archaeologists are amazed by the symmetry and precision with which they're designed ... each site is laid out with a large circle, a large square which would fit inside the circle, plus another circle. I figure there was some big chief who had a radius rope and a precise stride, plus they had figured out how to do equal diagonals to make squares, so not that amazed by the precision. But the work involved ... and the motivation? That's something to make you go hmmm. Aliens perhaps?!