Shinpōinyama Kofun group

The Shinpōinyama kofun group is located on a low hill at the confluence of the Tenryū River with the Ota River. The necropolis consists of over 30 tombs in various styles, which were arbitrarily divided into four groups, Group A through Group D, by archaeologists. Due to construction work, Group D was excavated in 1980. It was found to contain two keyhole-shaped tumuli and one square tumulus from the Kofun period and three graves from the earlier Yayoi period, along with a large amount of Yayoi period pottery shards. The two keyhole-shaped tumuli has lengths of 33 meters and 34 meters respectively.

The 34-meter tomb was excavated, and found to contain a stone-lined burial chamber in which gravel and clay are alternately stacked in holes of 8.1m from east to west and 5.6m from north to south. It contained stone sarcophagus with a wooden coffin. It was built in the first half of the 4th century, based on excavated earthenware, making it one of the oldest in the prefecture. Inside were numerous grave goods, including a bronze hammer, iron swords, and Chinese-made bronze mirror with a triangular rim and design of mythical animals, along with pottery from the early Kofun period.

The third tomb, a 12-meter trapezoidal-shaped tomb, and with the burial part in gravel, contained a sword and spear, and an iron casket, Earthenware (Haji ware) pottery from the second half of the third century was excavated.

The site is on a hill behind a Buddhist temple, with limited public access.

• List of Historic Sites of Japan (Shizuoka)

• Iwata city tourist information home page (in Japanese)