(32' x 20', IA-34-09) S. of Charles City, Riverton Township, Floyd County, IA. Shadow Av. S. 3.2 miles from jct with I218 exit 218 S. of Charles City to the crib on the E. side of the road at 2510. (N42 59.586 W92 40.252) Photo by Jack & June Schmidt 7-9-12.