Several of the exhibits at the Talbot Rice Gallery, Edinburgh, when we visited in February featured circles of different sorts, mostly of natural origin, but some not:-

Thios one has a depiction of Copernicus’s heliocentric solar system in the book at the centre:-

This was on the wall. It looks like the trace of an eccentically orbiting comet or something of that kind:-

Liesegang Rings. I confess I had only heard of Liesegang Rings in a chemical context before this but I now know they occur geologically too, as evidenced below:-