Yes, I vividly remember walking behind the falls. We have several photos in our family albums from behind the falls, along with a video or 2 of us behind them. It was closed off sometime in the mid 90's I believe. I always assumed they closed it off due to the fake rock structure that would/could crumble on guests due to safety concerns. I also remember it being a wood-chip path all the way around.
For several Christmas seasons they had a large house-like structure in the center of the pond area. It was synchronized to lights and a narrator over speakers played "Twas the Night Before Christmas." This structure was later moved to part of the train ride as one of the scenes you passed, the lights staying stagnate of course, with no narration.