If it's not too far out of your way, you might check out Bryce Canyon. I've been to Zion once, and Bryce twice. I didn't get tired of Bryce the second time, and I plan to visit it again. It's like being in another world. You can park in lots along the overlooks and hike on trails down into the formations. The air is thin, it's around 8000 ft elevation, but I felt great the two times I went there. It's exhilarating.