Valley of Fire on the way in. Ride in Zion NP. The Kolob section to the north is a sweet ass ride if you have never driven or been there too.

While it wouldn't be better than zion, the red rock canyon loop outside vegas is awesome. The scenic loop road. One way road, buttery smooth pavement, a great climb and fun twisty descent with excellent scenery. You can go further out to blue diamond area as well.