| Location | Nara Pref. |
|---|---|
| Shape | Round mound |
| Mound length | 109 m |
| Period | Late 4th c. |
Round mound ~109m in diameter in Nara City — Japan's largest round kofun and a National Historic Site (designated 2022). Dated to the late 4th century. In 2023, a serpentine sword (2.37m, Japan's longest) and a shield-shaped bronze mirror (1.26m, Japan's largest) were recovered, making global headlines. These finds represent the pinnacle of iron and bronze working in ancient Japan and testify to the extraordinary authority of the occupant. Finds are exhibited on a rotating basis at the Nara City Buried Cultural Property Research Center.
Serpentine iron sword (2.37m, the longest in Japan) and shield-shaped bronze mirror (1.26m, the largest in Japan), both from the projecting platform area. The main burial chamber (interior of the round section) remains unexcavated.
The February 2023 discovery of the serpentine sword and mirror — unprecedented in both scale and craftsmanship — was widely covered by NHK and international media. Nara City is continuing excavations in the surrounding area. About 15 min on foot from Kintetsu Tomio Station. The mound is relatively well preserved despite changes to surrounding terrain from agricultural reclamation. The Nara City Buried Cultural Property Research Center holds special exhibitions of the finds; check before visiting. As the largest round kofun in Japan, it is a rare example of a grand circular mound built during an era when keyhole and scallop-shell mounds dominated — attracting considerable scholarly interest.