One highlight (recommended if you ever visit here) was a ranger-led walk through somewhere called 'Fiery Furnace'. This is an area where the cracks between fins (see geology lesson below) are narrow, and involves a lot of clambering up and down through some very tricky terrain. It brings out the child in the adult, not recommended if you have nightmares about getting stuck between big rocks. In the process you get to learn about the geology and the local flora and fauna. The latter are all interesting for the various strategies that they use to get by on 9 inches of rain per annum (remembering that as much as 0.5 inch of that can fall in one 20 minute period). 

Finally, Geology lesson time (we'll make this quick). Big ocean, keeps drying up, so eventually umpteen thousand foot thick salt deposit. Then, a mile depth of sandstone deposited on top. The pressure starts the salt moving underneath - it oozes like toothpaste. Eventually it encounters a fault, and all along the fault, the sandstone is pushed upwards. Cracks form along the bulge - see diagram below - leaving long thin walls of sandstone known as fins. Erosion makes holes in the side of fins, leaving arches.