Jinbayama Kofun: A Keyhole Tomb on the Ayaragi River Terrace
Jinbayama Kofun (仁馬山古墳) is an early Kofun-period keyhole-shaped burial mound, or zenpo-koen-fun, in Nobuyuki and Aritomi, Shimonoseki City, Yamaguchi Prefecture, designated a national Historic Site in 1991.
According to the Agency for Cultural Affairs, the tomb sits on the Go terrace on the right bank of the Ayaragi River, which flows into the Hibikinada Sea north of central Shimonoseki. It follows the southern edge of the terrace with its square front facing west. Jinbayama Kofun is 74 metres long, with a round rear mound 46 metres across built in 3 tiers. The front section is short and small, about half the diameter of the rear mound in width.
The name is read Jinbayama in the Agency's database; the Shimonoseki City Archaeological Museum writes it as Jinmayama.
Why It Was Designated
The Agency notes that among the many tombs around the Go terrace, including the Wakamiya tombs within the Ayaragi-go Site, Jinbayama Kofun is thought to be the oldest, which makes it key to understanding how tomb building developed in the area. North of the front mound is a hollow that may mark a moat, and 2 small round mounds are thought to be subsidiary tombs.
The designated area also takes in the Uematsu Kofun, about 70 metres to the northeast, the only square tomb in the old Nagato province and built at about the same time.
The Shimonoseki City Archaeological Museum says the mound was identified as a gourd-shaped tomb in 1902 and named during a survey in 1921. Excavations between fiscal 2005 and 2008 found, beneath the rear mound, a clay enclosure around a split-log coffin estimated at 6.2 metres long, apparently never robbed. The museum dates the tomb to the late 4th century, gives its length as 74.8 metres and the rear mound as 47 metres across, and reads its cylindrical and jar-shaped haniwa as signs of strong ties to the Yamato court.
What to Look For
The museum reports that scrub around Jinbayama Kofun has been cleared, so the mound can now be seen from the plain to the south. Its keyhole outline is well preserved; step back to take in the whole shape, the tiered rear mound and the stubby front.
The Agency's description records no facing stones or haniwa, yet later excavation produced haniwa. Reading the two side by side shows how research on the tomb has moved on.
Visiting Jinbayama Kofun
Jinbayama Kofun is an outdoor site, and no official visiting hours or fees are published. The nearby Shimonoseki City Archaeological Museum serves as the guidance centre for the local heritage trail and displays finds from the area. It opens from 9:30 a.m. to 5:00 p.m. (last entry 4:30 p.m.), closes on Mondays and over the New Year, and the permanent exhibition is free.
The museum is about 5 minutes on foot from Kajikurigodai Station on the JR San'in Line, or about 20 minutes by car from the Shimonoseki interchange of the Chugoku Expressway. The mound may border private or farm land, so check at the museum which areas are open before you go.
- 📍 Plan Your Visit to Yamaguchi
- Find tours, activities & transport passes near Jinbayama Kofun
- [ Kintaikyo Bridge & Hagi Castle Town Tours ]
Q&A
- How big is Jinbayama Kofun?
- The Agency for Cultural Affairs gives a length of 74 metres and a rear mound 46 metres across. After excavation, the Shimonoseki City Archaeological Museum gives 74.8 metres and 47 metres.
- When was Jinbayama Kofun built?
- The Agency considers it the oldest of the tombs around it. The Shimonoseki City Archaeological Museum dates it to the late 4th century, in the early Kofun period.
- When was Jinbayama Kofun designated a Historic Site?
- On 15 May 1991. The designated area also includes the Uematsu Kofun about 70 metres to the northeast.
- How is the name Jinbayama Kofun pronounced?
- The Agency for Cultural Affairs database reads it Jinbayama; the Shimonoseki City Archaeological Museum writes Jinmayama.
- Is there a museum near Jinbayama Kofun?
- The Shimonoseki City Archaeological Museum covers the area's sites. It opens from 9:30 a.m. to 5:00 p.m., closes on Mondays, and the permanent exhibition is free. It is about 5 minutes on foot from JR Kajikurigodai Station.
Basic Information
| Name | Jinbayama Kofun (仁馬山古墳) |
|---|---|
| Location | Nobuyuki and Aritomi, Shimonoseki City, Yamaguchi Prefecture |
| Designation | Historic Site |
| Year Designated | Designated 1991/5/15 (Heisei 3) |
| Quantity | 1 site (including the Uematsu Kofun) |
| Dimensions | 74 metres long, rear mound 46 metres across (Agency for Cultural Affairs) |
| Owner | Not listed in the Agency for Cultural Affairs database |
| Public Access | Outdoor site. No official hours or fees published |
References
- Agency for Cultural Affairs Database: Jinbayama Kofun (Japanese)
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/2445
- Cultural Heritage Online: Jinbayama Kofun (Japanese)
- https://online.bunka.go.jp/heritages/detail/162258
- Shimonoseki City Archaeological Museum: Heritage Trail (Japanese)
- https://www.shimo-kouko.jp/exhibition/shisekinomichi/
- Shimonoseki City Archaeological Museum: Visitor information (Japanese)
- https://www.shimo-kouko.jp/user-information/%e6%9d%a5%e9%a4%a8%e6%83%85%e5%a0%b1/
Last verified: 2026.09.27