The most beautiful part of the route, for me, came early on the second day, when the train followed the course of the Colorado River. There were groups of people down there, floating/boating/cavorting, and when the first of them spotted the train, they turned, dropped their shorts, and mooned us. Then, the second group did the same thing. Then the next, and the next; and for two hours, the Colorado River was a parade of bare butts. These were not modest moonings! They were enthusiastic; well-practiced; italicized by the merry slapping of cheeks.