Formed by the collapse of the hillside over the stream bed; the water eventually washed out the rubble, leaving a rock-vaulted passage 400 feet long and 15 feet high. In summer, tiny streams trickle through the passage. In spring, freshets roar through the tunnel. The stream above the cave is called Devil Creek, and from it a 75-foot waterfall leaps far beyond the edge of the cliff, forming an aquatic arch over the trail.