There is a really neat, albeit remote little place in Zion National Park in Utah called The Subway, where water has carved a tunnel through the rock over the ages. It is an all day venture to hike there, but well worth it.
Just don’t get caught in there during a rain storm!
Water flowing through “The Subway”, Zion National Park, Utah, USA. Canon 1Ds. Mark II. 16mm. ISO 100. f/13 @ 1.3 seconds. Polarizer.