Hopewell Culture National Historical Park contains earthworks in the form of squares, circles, and other shapes.
From about 200 BC to 500 AD, the Ohio River Valley was a focal point of the prehistoric Hopewell culture. The term Hopewell describes a broad network of beliefs and practices among different Native American groups over a large portion of eastern North America. The culture is characterized by the construction of enclosures made of earthen walls, often built in geometric patterns, and mounds of various shapes.
The most striking Hopewell sites contain earthworks in the form of squares, circles, and other geometric shapes. Many of these sites were built to a monumental scale, with earthen walls up to 12 feet high outlining geometric figures more than 1000 feet across. Conical and loaf-shaped earthen mounds up to 30 feet high are often found.