Check out miobi.org... that place is awesome... in relation to C.R. it's probably 2 1/2 hours from you, up around Knoxville/Albia area.
Well worth the trip though! I've always had a ball there... I'm in Wayland, IA... about 10 mins from Washington, and around an hour from CR...
MIOBI is an old strip mine... dunno how many acres... rocks, hills, mud, water... and everybody's really laid back and cool to hang with. Memorial Day Weekend is the next public event... other than that - there used to be a place right around CR called 600(?) Acres??? Thought it was around Marion... might do some searches on that... Good luck!!! Holler at me if you're ever around Washington, Mt Pleasant, or Wayland.... firstname.lastname@example.org