Here's a recent photo of the Devil's Kettle waterfall in Judge C.R. Magney State Park, located roughly halfway between Grand Marais and Grand Portage, MN. This waterfall is really unique in that it splits into two channels and one of the channels (the one on the left in this photo) plunges into a hole in the rock and nobody knows where it comes back out. The channel on the right drops into a pool and continues to flow downstream. It is a curious and fascinating thing to ponder, where that hole in the rock goes and where the water that drops into it ends up.