The Sannai Maruyama Site is a settlement site of the Jomon period about 5900 to 4200 years ago, and has been a sedentary life for a long time.

Archaeological excavation from 1992, pit building traces, large pit building traces, adult graves, children's graves, embankments, pit building traces, large pit building traces, storage pits, clay mining pits, dumps, roads Traces were found, and the state of the entire village and the natural environment at that time were concretely understood.
In addition, a huge amount of Jomon pottery, stone tools, clay figurines, clay and stone accessories, wooden tools (digging sticks, bag-shaped knitting, knitting cloth, lacquer ware, etc.), bone tools, jade and obsidian brought from other areas, etc. Has also been excavated.

Many discoveries have changed the image of Jomon culture, such as the excavation of cultivated plants such as gourds, burdock, and beans, and the clarification of chestnut cultivation by DNA analysis.
In November 2000, it was designated as a national special historic site.