From Ohio History Central
The Hopeton Earthworks site is a large Hopewell culture (100
BC -- AD 500) ceremonial center located along the Scioto River in Ross County. It includes a large circular enclosure, 1,050 feet in diameter, attached to a square about 900 feet across. Originally, the walls were 12 feet high, but years of cultivation have reduced their height to less than five feet.
The Hopeton Earthworks are situated just across the Scioto River from the Mound City Group and a set of parallel walls extends from Hopeton towards the river. It is likely that these sites were closely related during Hopewell times.
The Hopeton Earthworks site is a National Historic Landmark and is part of Hopewell Culture National Historical Park.