The American Falls, as seen from Niagara Falls, New York.
The slight yellow cast you see on the falls is a result of the stunning sunset that was just starting... based on my photos, I'm guessing the gorgeous colour and light lasted maybe 5 minutes maximum. Then the falls became darker and darker as night fell.
Wow! This is beautiful! I've always felt a certain exhilaration around waterfalls, as if I am falling with the water, and this picture invokes that very feeling. Great job!