Indiana Jones was here
One of my top four national parks from the whole trip, this. Arches National Park (nps link, wiki link) is just full of amazing natural rock features, including, unsurprisingly, some pretty impressive arches.
The very first scene in Indiana Jones And The Last Crusade is shot from almost exactly this spot - something I didn't realise at the time! In fact, what we're doing at this stage is fixing a flat tyre.