This is the spot where Andy and Opie were when Opie picked up the rock and threw it in the lake in the opening credits of The Andy Griffith Show. The water has gotten lower so there's no longer a lake where the rock would have landed. The water level was lowered to reduce pressure on the earthen dam.
Wikipedia article:
http://en.wikipedia.org/wiki/Andy_Griffith_ShowCategory:
television Not approved