I vaguely remember reading a story, I think it was Louis L'Amour, where the characters rode thru a creek (maybe even a waterfall) to a hidden spot. There was a cave that you could ride thru, but you had to turn at just the right moment or you would fall to your death. I think that this may have be a Milo Talon story? My memory just isn't helping me enough to recall it exactly.
#4. "RE: Help me find this story" In response to Reply # 0
The Short Story 'Rustlers Roundup" has a "scene" where Finn Mahone guides the female interest across a shale outcropping where the horse's steps had to be counted, and a turn towards a tree landmark to exit the slide. And I have a ghost of a memory of the protagonist crossing a body of water, led by a castaway, counting steps between turns to avoid dropoffs. Possibly Fair Blows the Wind, Sackett's Land, or To the Far Blue Mountains.