Hilltop enclosures with piled rock walls are on a hilltop, but have a circular piled rock wall instead of core veneer rubble filled. While they were difficult to get to, their primary purpose does not appear to be defense. There is a consistency to these sites.
A general overview of Hilltop Enclosures is presented in this video.
There were at least 3 petroglyph boulders showing people doing things that may be related to what happened inside the circle.
Natural hill encircled by terrace which is encircled by piled rock wall. There were very few artifacts.
3D version shows hill better.
There was a petroglyph boulder inside the circle.
The rocks weren't suitable for petroglyphs at this site. There were cliffs along the bottom and tallus slopes going up the steep sides making it difficult to climb.