On the day we went to see the Great Serpent Mound, the rain plunged from the sky. Lightning shot down to the cornfields and made the cornfields roar. Everything was dark. Guides recommend that you come to the Serpent early or late in the day, when shadows alongside it are deep and the winding shape becomes bolder. But on the day we visited, the whole of Ohio was shadow, save the neat green grass of the Serpent’s skin, which was oddly bright.
When the first European settlers came to farm southwestern Ohio, they found earthen lumps scattered all around the land. They did not know what these lumps could be — some farmers went about flattening them, others farmed around them. In the 1840s, a local doctor and a newspaper editor from the town of Chillicothe investigated the mounds. They discovered wooden structures inside, built to house the dead of Native tribes whose names are lost to us now. Jewelry and effigies were placed around the cremated remains to keep the spirits company. Then the Mound Builders covered over the structures with layers of soil and sand. As the generations passed, new dead were buried on top of the old, and more earth was put on top, until the mounds grew higher and higher and the little wooden structure collapsed within.
more here.