The West Virginia. Cyclopedia
Sacred circles are often located near Adena burial mounds, in some cases encircling them. This suggests that they served ceremonial purposes, possibly related in some way to the rituals practiced at the burial mounds, such as serving as a ceremonial gathering place.
In 1976, archaeologists from the West Virginia Geological and Economic Survey excavated test trenches at the base of Grave Creek Mound to verify historic accounts of a moat or ditch surrounding the mound. Test trenches showed that the moat was a nearly-symmetrical construction, measuring 40 to 45 feet wide, 4 to 5 feet deep, and 910 feet in length around the mound.
Additional information on the 1976 excavations.