I think that waterfalls can be a very beautiful subject in photography. When the running water is combined with a long exposure shot, the water leaves a very smooth and soft trail, giving the impression of elegance and beauty.

In this photo, taken by BrooklynBoy1968 (Flickr) i like how the density of the water varies across the waterfall. I think the combination of big falls and small ones makes for a very deep image. The contrasting rocks in the background makes the falls stand out very well, and the reflections in the surface of the water at the bottom are very impressive.