Jinyama Burial Mound Group: Where Japan's Four-Cornered Yayoi Tombs Began
On a wooded ridge above the Babai River in the city of Miyoshi, five low earthen mounds lie strung along a north–south axis, four of them squared neatly into a single plot. They are easy to miss. Yet these unassuming features, excavated in the late 1970s ahead of a city road project, preserve the earliest known examples of a tomb form unique to ancient western Japan — the yosumi-tosshutsu-gata funkyū-bo, or "four-cornered protruding burial mound."
The five mounds rise on a low hill in Shijukkan-chō and Mukaeda-chō, just below 300-meter Mount Jinyama. They were designated a National Historic Site on December 20, 2000 — Notification No. 194 — under the Agency for Cultural Affairs criteria for shell-midden, settlement, kofun and related remains. Together they span roughly 40 meters north–south and 8 meters east–west: a tightly clustered cemetery rather than a sprawling monument complex.
A tomb form invented in the Miyoshi basin
The four-cornered protruding mound is, at first glance, a square or rectangular earthen platform — but its four corners are pulled outward into long, tongue-like projections, giving the plan view the shape of a starfish or a wide-armed cross. In the Chūgoku mountains the slopes were faced with river stones (haritsu-ishi) and the foot lined with cut stone. The form was used only for the burials of community leaders, and only between roughly the 1st century BCE and the mid-3rd century CE, before the keyhole-shaped kofun mounds that came to define the next era.
About 110 such mounds have so far been identified, scattered across the inland Chūgoku range, the Sanin coast of Shimane and Tottori, and the Hokuriku coast as far as Toyama. The very oldest examples — those that show the form still finding its shape — are concentrated here, in the Miyoshi basin. Jinyama is the textbook case.
What makes the site so valuable to archaeologists is precisely that none of the five mounds is "finished" in the canonical sense. The stone-facing technique varies from mound to mound. So does the prominence of the four corner projections, the scale of the platform, and the type of burial chamber inside. Mound No. 3 carries the clearest, most exaggerated corner extensions; others are barely tapered. The builders were not following a fixed template. They were inventing one.
Reading the five mounds
The cemetery falls into two parts. Mound No. 1 was built first, on its own alignment, and ended up partly buried beneath the later embankment of Mound No. 2. The remaining four — Nos. 2 through 5 — were then laid out in a single planned plot, arranged in a near-straight line on a shared axis. The shift in orientation between Mound 1 and the rest suggests a deliberate break: a first generation of leaders followed by a second who chose, consciously, to do things differently.
All five graves yielded Shiomachi-type earthenware, the diagnostic pottery of the late middle Yayoi in this region, conventionally placed in the 1st century. That tight dating means the entire group was raised over a short span of time — perhaps only one or two generations of local chiefs. For a single small ridge, that is a remarkable concentration of authority.
From here the tomb form moved north and east. By the Late Yayoi period it had been adopted by communities in Hōki and Inaba (modern Tottori), and by the late Yayoi the great rulers of Izumo were building four-cornered mounds on a far grander scale. The Hokuriku versions, on the Japan Sea coast, dispensed with the stone facing entirely. The lineage runs from Jinyama outward.
Visiting the site
The mounds themselves sit on a quiet rural ridge, reached most easily by car. Visitors arriving at JR Miyoshi Station on the Geibi Line can reach the site in about 11 minutes by taxi. There is no on-site museum or major visitor infrastructure; the area is signposted, with information boards near the burial group itself.
For context, the visit makes most sense paired with the Hiroshima Prefectural Museum of History and Folklore — the Miyoshi Fudoki-no-Oka Museum — about ten minutes' drive to the southeast. The museum's permanent display covers the prehistory of the Chūgoku mountains and the Gō River basin, including Shiomachi-type pottery of the kind excavated at Jinyama and Important Cultural Property finds from the nearby Yadani Kofun, which itself preserves an unusual double four-cornered form. The museum opens 9:00–17:00 (last entry 16:30) and is closed Mondays and the New Year period.
The Miyoshi basin, taken as a whole, holds more than four thousand recorded burial mounds — one of the densest concentrations of ancient graves in western Japan. The neighboring Jōraku-ji and Nanatsuzuka kofun groups, with 176 designated mounds preserved as parkland, give a sense of what came after Jinyama's experimental beginnings.
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Q&A
- Why is Jinyama considered the origin of the four-cornered burial mound tradition?
- The five mounds at Jinyama date to the late middle Yayoi period (around the 1st century) — the earliest secure dates known for the form. Just as importantly, their construction varies from grave to grave: the stone facing, the four-corner projections, and the burial chambers were all still being worked out. Archaeologists read this lack of uniformity as a sign of a tradition in the process of being invented.
- Can the mounds be seen at the surface today?
- The site is preserved on its original ridge with explanatory signage, but it is a quiet rural location rather than a developed park. The mounds read as low grass-covered platforms; the dramatic four-corner shape that comes through in archaeological diagrams is much more subtle on the ground. Visiting the Fudoki-no-Oka Museum first helps the eye know what to look for.
- What is Shiomachi-type pottery, and why does it matter here?
- Shiomachi-type is the standard pottery sequence used by Yayoi specialists to date sites in this part of northern Hiroshima. Its appearance in all five Jinyama graves is what allows researchers to confidently place the mounds in the 1st century and to argue they were built within a short window.
- How does Jinyama relate to the keyhole tombs that came later?
- The four-cornered mound was a parallel tradition, not a direct ancestor. While the chiefs of Yamato in central Japan were beginning to build keyhole-shaped zenpō-kōen-fun, communities along the Japan Sea and through the Chūgoku mountains used the four-cornered form for their rulers. By the mid-3rd century the keyhole shape became dominant nationally and the four-cornered tradition came to an end.
- What else is worth seeing nearby?
- A natural circuit is to combine Jinyama with the Miyoshi Fudoki-no-Oka park, the Jōraku-ji and Nanatsuzuka kofun groups (a designated National Historic Site with 176 surviving mounds), and the Yadani Kofun, whose excavated grave goods are designated Important Cultural Property. All sit within a short drive of one another in the Miyoshi basin.
Basic Information
| Name | Jinyama Burial Mound Group (陣山墳墓群) |
|---|---|
| Reading | Jinyama Funbo-gun |
| Designation | National Historic Site (Notification No. 194) |
| Designation date | December 20, 2000 |
| Designation criteria | Shell middens, settlement remains, kofun and related sites |
| Period | Yayoi period, late middle phase (around the 1st century) |
| Composition | Five four-cornered protruding burial mounds (Mounds No. 1–5); north–south extent approximately 40 meters, east–west width approximately 8 meters |
| Excavated materials | Shiomachi-type earthenware from all five mounds |
| Location | Shijukkan-chō Jinyama and Mukaeda-chō Hinome, Miyoshi City, Hiroshima Prefecture |
| Access | About 11 minutes by car from JR Miyoshi Station (Geibi Line). Best combined with a visit to the Miyoshi Fudoki-no-Oka Museum. |
References
- Agency for Cultural Affairs, National Cultural Properties Database — Jinyama Burial Mound Group
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/3273
- Cultural Heritage Online — Jinyama Burial Mound Group
- https://bunka.nii.ac.jp/heritages/detail/192512
- Miyoshi City Official Website — Jinyama Burial Mound Group
- https://www.city.miyoshi.hiroshima.jp/soshiki/49/3522.html
- Hiroshima Prefectural Board of Education — Jinyama Burial Mound Group
- https://www.pref.hiroshima.lg.jp/site/rekimin/syuhen-jinyama.html
- Hiroshima Prefecture Cultural Properties — Jinyama Burial Mound Group
- https://www.pref.hiroshima.lg.jp/site/bunkazai/bunkazai-data-106120220.html
- Miyoshi Fudoki-no-Oka Museum (Hiroshima Prefectural Museum of History and Folklore)
- https://www.pref.hiroshima.lg.jp/site/rekimin/
Last verified: 2026.05.16