In part of the National Park is the Painted Desert:
Very blue and red exposed hillsides, called the "Blue Tepees."
Petroglyphs on the side of a rock. Native Americans made these sometime in the last two thousand years. You can only really see these with the help of binoculars or zoom lens (there are free viewing scopes set up so you can see):
Chunks of petrified trees, dating from the Triassic age:
Close ups of the wood (now made up of agate, jasper, and other such rock):
The Agate Bridge. It was reinforced with concrete in 1917, but yes, this is a whole petrified trunk (34m / 110 feet long), preserved from millions of years ago, that was found lying across the gully.
Pretty cool stuff!
If you visit, don't take any petrified wood pieces. A number of people apparently mail back pieces to the National Park Service, and a lot of them say they had bad luck for taking them
! Anyway, you can buy lots petrified wood from the gift shops or other such shops nearly - which is from privately owned land (and hopefully no curse 
).The whole park is pretty big. Make sure you have at least three hours to go through it, and enough spending money for souvenirs! More information here:
http://www.nps.gov/pefo/index.htm
