The Great Serpent Mound is a 1,348-feet-long, three-feet-high prehistoric effigy mound located in Peebles, Ohio. It was built on what is known as the Serpent Mound crater plateau, running along the Ohio Brush Creek in Adams County, Ohio. The mound is the largest serpent effigy known in the world. The first published surveys of the mound were by Ephraim G.