The Lower Falls of the Yellowstone River in Yellowstone National Park.
I ended up visiting the Lower Yellowstone Falls three times during my week in YNP. I still didn't go on all the trails or see all the viewpoints by a long shot. There are trails taking you near the base and also trails taking you to the brink. The amazing thing is that the falls and resulting canyon are so immense and breathtaking that you don't really notice the trails or the people. Late September in full sun is probably not the best time to photograph the falls as they seem to be in constant shadow one way or the other. My best shots are probably when I was there the last time late in the day and the camera was basically looking right into the teeth of the sun. Regardless, the place is spectacular and here are my best efforts to take the the portraits of both the upper and lower falls. Click on an image for a larger file to view and thanks for looking.
The lower falls on my first visit early in the morning. Notice the viewing area right at the brink to the upper right of the falls in the photo. That will give you some perspective on size.
This is looking back at the canyon carved by the river from the Artist's viewpoint. Only the Grand Canyon in Arizona is a more impressive canyon that I've ever witnessed.
The upper falls.
A couple views from Uncle Tom's trail. Starting in 1898 Tom Richardson was one of the first people to construct a trail into the canyon for people to get a better view of the falls. He used rope ladders and wooden steps as well as provided a meal for the day long excursion, all while making a nice profit from each tourist. Luckily there are steel and cement stairs now and as long as you paid to get in the park, the hike is free. I realized on the climb back up just how much of a flatlander I really am though!
The famous view from the Artist's viewpoint.