John day painted hills
The Painted Hills at the John Day Fossil Beds are one of the more unique places I have ever visited (listed as one of the 7 wonders of Oregon). The painted hills are only about a square mile, but offer tons of interesting photographic opportunities.
The location is a long drive from any large town and is not easy to get to. However, I would highly recommend making the time and effort, as you will be rewarded with some great photographs.