Somewhat removed from the structures, there is a stone circle, actually consisting of two circles of stones, one within the other, over ten feet in diameter. The outermost ring is made up of twelve stones worked to be curved. Archaeologists who have studied it consider it to have been a mill. The archaeologist Ken Feder notes that unlike European stone circles the stones are recumbent and not upright and identifies it as a bark mill used to extract tannin for leather making. Walking in a circle animals would pull the mill wheel between the double circle of stones." Other researchers have hypothesized it is a Native American built structure.