The Ōyu Stone Circles was used for about 500 years. But within that time, it seems that the two large stone circles were completed in the first 200 years, and in the following 300 years, many “Remains of a circular stone alignment” were built.

The Ōyu Stone Circles was a large-scale project involving many different villages, so it’s plausible that some villages joined midway. However, if the two stone circles were a planned project and each village already had its assignment, there wouldn't have been space for groups who wanted to join in later on. So it’s said that those groups were given the ring-shaped stone structures to build.

Also, each stone circle has what’s called a “Row of stones”. Looking at the various stones in the Ōyu Stone Circles from a birds-eye view, the two stone circles are only a part of the whole and it may be that they were trying to draw something like the Nazca Lines. What does it look like to you?