Quite a while back I traveled the American West.
Visiting National Parks and State Parks, I was immediately fascinated by the petroglyphs, rock carvings that removed the darker surface of the rock and exposed the lighter colored rock beneath. Some of them have been carved thousands of years ago, most of them are at least 400 years old and still clearly visible on many rock faces. You can find them in Arizona, Utah, New Mexico, Colorado and many more places.
As many artists do when they see the works of other artists, I played with the shapes and filled them with my own symbols and patterns.