The petroglyphs in this park are aged at about 1000 years old and they were done by the Fremont people. My favorite was the lizards and the ram!
It is hard to be scale in these photos but the lizard in the center left of the first image is almost 6 feet long!
This lizard is about 40 feet up the wall.
The one above is weird but the next one is kinda creepy!
All the above petroglyphs are in the part of the park accessible from Utah (the part with the dinosaur quarry). Below is one from a wall in the canyons area in of the park located in Colorado. There were a bunch of similar ones but they were 35 feet up and hard to see.