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.
Cherry Tree, Kyoto, Japan The cherry blossoms are the most beautiful tree flowers in the entire world, according to me. They completely drench the tree in a soft pink, and I've never seen something more gorgeous.