Somehow we missed this on the way up.  The guide book says, "You'll come to a psychedelic eye.  Head up the left bank to the first pool and waterfall."  The eye was apparently done by modern day artists in the 70's... no doubt a refugee flower child with nothing better to do but deface a rock.  I'm sure some future archeologist will find this and draw some far out conclusion about the society that lived around here.