3. The Trough.  Much earlier in the hike we saw a couple people wearing hard hats.  It seemed odd at the time, but when we got to the trough we knew why.  This is the part of the hike I thought was the most dangerous.  People up ahead were knocking loose small rocks, and they picked up quite a bit of momentum as they rolled down the trough.  Notice the bull's-eyes painted on the rocks to help guide hikers along the best path.