I've been to Niagara Falls more times than I can count, and it is ALWAYS simply incredible. I've stood by the falls for hours, until soaked by the spray. I've also been there when the smaller section (The American falls) was frozen.
Image by Mike Hollingshead: An amazing supercell tracks across southern Nebraska, producing other-worldy storm structures. At times, this storm looked like a giant tsunami in the sky. The supercell formed after two supercells merged near McCook Nebraska.