Just outside of Billings is Pictograph Caves State Park.
A short hike up the hill, and you are looking at drawings that have been in the caves for thousands of years.
Unfortunately, the visitor’s center was closed by the time we came down off the hill, but we still learned a lot about the caves.
The kids collected rocks from the trail that they were convinced were as old as the cave drawings. With pockets full of sparkly rocks, they went down to climb the trees at the picnic area. Not a bad way to end the day.