Ruins have been found near the path to Himemiya Shrine.
This would be the line of large caves you see. Though some of them of rather small, they are thought to have been closed off by boulders in the past. These are thought to be graves for ordinary people, with each cave belonging to a household and often storing generations of a family.
Scattered about here is obsidian rock and fragments of earthenware used in the past. Though you can pick them up for a closer look, be sure to return them where they belong.