In the Ohio River Valley, earthen mounds and embankments forming huge geometric enclosures were built by Native American hands almost 2,000 years ago. Hopewellian people gathered at these earthworks for feasts, funerals, and rites of passage, and these monumental structures were sacred spaces in the lives of these American Indians. The area lies in a humid continental zone with a generally temperate climate, with mildly cold winters averaging around 30 degrees Fahrenheit, hot and humid summers averaging around 75 degrees Fahrenheit, average annual rainfall just under 38 inches, and generally light winter snowfall averaging less than 24 inches.