The earthwork, built about 2,000 years ago, is a walled enclosure made of soil on top of a flat summit. It is higher than nearby portions of Ohio Brush Creek and 800 higher than the Ohio River. It was made by the Hopewell people. It is over 1½ miles in circumference, enclosing . Thirty-nine man-made openings occur throughout the enclosure: thirty-six that are verified as being made by Indians and three others still unknown as to how they were made. The wall is 6-15 feet high and its total length is . It is 30 feet wide at its base in most areas. Archaeologists believe it was not used as a fort, but instead as a religious site.