This is an underwater site from the initial Jomon period that was found at the bottom of Lake Suwa. Large quantities of arrowheads made from obsidian were produced at this site. The arrowheads excavated from this site give us an insight into the refined and excellent craftsmanship of the Jomon people. Articles excavated from this site are stored and on display at the Suwa City Museum. This site has been designated a Nagano Prefecture Important Site and a Suwa City Historic Site.