Ofune Ruins are located on the hill on the left bank of the Ofune River in Ofune-cho, Hakodate City, Hokkaido. These are the ruins of a large-scale colony in the middle Jomon period (between four and five thousand years ago). The site was designated as a national Historic Site in 2001.

The site is blessed with fine natural surroundings with Funka Bay in front, Mt. Kurinokiyama in back and the Ofune River, where salmon and trout swim upstream. In the excavation research carried out in 1996, large pit dwellings, the remains of mounds, flask-shaped holes that are considered to have been used for food storage were discovered. The total area of the site is 72,000 square meters, where more than 1,500 pit dwellings are expected to have existed. The characteristics of the relics are that pit dwellings were large in size and that stone plates are large in number. As many as 2.000 stone plates were dug out in the research of only one year. Ofune Ruins have attracted attentions as the center of the cylindrical earthen vessel culture.