You've gotta see the Grand Canyon at least once in your life.

And go down into it. Standing on the rim, with nothing seeming to move, it looks like you're just looking at a painting. There's definitely nothing wrong with that, because it's beautiful, especially at sunrise. But start down one of the paths, probably Bright Angel, and you'll find that the Canyon comes to life. Dress properly, bring plenty of water. That's the main thing. Remember it takes twice as long to come back up as it did to get down, so consider that when you decide how far down you want to go.