Aside from the obvious beauty, we were drawn mainly to Zion National Park after reading about 'Number 5 - Hiking the Narrows' in a National Geographic survey of the Top 100 adventures in the United States.
Zion is often compared to the Grand Canyon in terms of its dramatic scenery, deep cutting gorges, and colourful sandstone rock-faces. The difference of course is that Zion's canyons are all raised from the main tourist thoroughfares, whereas the Grand Canyon mainly sinks down.
The highlight for those hankering for an arduous day out is to trek the Virgin River Narrows; a 17 mile journey through a narrowing canyon with the river bottom acting as your trail. It can be pretty hairy in stages. Think of it as a long day out craning your neck skywards for half the day, and the other half is spent walking on slippery bowling balls! Remember to take a dry-bag, set out early, and go for the full 16 miles in one day ... awesome experience! Those wanting a more leisurely experience can book a site and camp half way. I must admit, from the camp sites we saw it probably would rank up there in best camping locations in the world with the remote setting, the flowing river lulling you to sleep and the great temperature.
On the second day, we decided to hike up to the top of Angel's Landing in 100 degree temperatures. Excellent views from the top capping off a fantastic trip to this national park. A must do for all travellers visiting the Utah / Arizona area.