This canyon has to be one of the most beautiful places in the park. If you rush through just to get the hike done you'll miss half the intriguing features of the canyon. The fifth bridge has been washed out by high water this spring. Some of the maps show starting at the fifth bridge but that is no longer possible as you will not be able to get across the river. The best trailhead is at the second bridge. I recommend traveling as far as the fourth bridge then returning to the first bridge and back to the beginning. It was especially interesting to watch for underground rivers dumping into the main river below the fourth bridge these underground rivers apparently drained from Medicine Lake upstream through underground limestone tunnels. I would recommend giving yourself a minimum of two hours to fully enjoy the hike.