A Settlement on the Edge of the Inland Sea
Eight meters above the left bank of the Kurokawa River, on a low terrace that looks north toward the Suo-nada Sea, the Kobe Site (Kobe Iseki, 小部遺跡) preserves the traces of a village built in the late 3rd century and abandoned roughly a hundred years later. The 13,508-square-meter site, located in Araki, Usa City, in northern Oita Prefecture, was identified during construction work in the late 1960s. Half a century of excavation has since revealed something rare: a settlement whose layout changed in clear, datable stages, taking it from a fortified community to an elite residence and, finally, to a burial ground.
For these reasons, the Agency for Cultural Affairs designated Kobe as a National Historic Site (国史跡) on March 26, 2021, with additional land added in March 2025. It is the sixth nationally designated historic site within the city of Usa.
The Moated Village
When the settlement first appeared at the opening of the Early Kofun period, it was surrounded by a deep ditch enclosing roughly 120 meters north to south and over 100 meters east to west. The outline took the form of a rounded square. On its southern edge, the ditch extended outward into two square projections, each about 10 meters across, whose function is still debated. A row of wooden posts ran parallel to the ditch on its inner side, reinforcing the enclosure.
Moated settlements of this period are not unusual in western Japan, but few have been excavated thoroughly enough to show how their internal arrangement evolved. Kobe is one of the exceptions.
From Village to Residence
In the first half of the Early Kofun period, the inhabitants laid out a smaller rectangle inside the original enclosure. Roughly 50 meters north to south and 37 meters east to west, this inner space was set off by another line of posts. Along its western edge stood a large raised-floor building, four bays long and three bays wide, measuring 8 meters by 5.6 meters. The interior contained additional pillars, suggesting an elevated wooden floor of a kind associated with high-status structures.
The shift is more than architectural. The community had drawn a fence around itself, then drawn a second fence inside the first, reserving the central space for a select few. Archaeologists describe the result as a 居館 (kyokan), the residence of a regional chief.
Then, sometime in the second half of the period, the whole arrangement was dismantled. Square moated tombs about 10 meters on a side began to appear across the area. The place of the living had become a place of the dead.
Pottery from Across the Inland Sea
Within the ditch fill, excavators recovered large quantities of pottery whose shapes and decoration point away from northern Kyushu. Vessels of styles associated with the Kinai region around present-day Nara and Osaka, and with Kibi in present-day Okayama, appear in numbers that cannot be explained by occasional contact. Some of these vessels are on permanent display at the Oita Prefectural Museum of History in nearby Takamori.
The plain on which Kobe sits opens directly to the Suo-nada, and from there to the broader Seto Inland Sea. For people moving goods, ideas, and political alliances along that maritime corridor in the 3rd and 4th centuries, this stretch of coast was an obvious landfall. The pottery suggests Kobe served as one of the nodes where those exchanges came ashore.
The Akatsuka Connection
Roughly contemporary with the residential phase at Kobe, a keyhole-shaped tumulus was built about two kilometers to the east, on a different terrace overlooking the same plain. Akatsuka Kofun, 57.5 meters in length, is the oldest of the six keyhole tombs that make up the Kawabe-Takamori Tumulus Cluster and one of the earliest examples of the form in all of Kyushu. When it was opened in 1921, the rear circular chamber yielded five bronze mirrors of the type known as 三角縁神獣鏡 (triangular-rim deity-and-beast mirrors). Four were cast from the same molds as mirrors found in tombs near the Yamato heartland in Kyoto and northern Kyushu, suggesting a direct relationship with the emerging central polity.
The timing is too close to ignore. The people who lived behind the fences of the Kobe residence may well have been the same lineage whose senior figures were laid to rest beneath Akatsuka. Read together, the two sites sketch out a complete cycle: where regional elites lived, how they organized space around themselves, and how they were buried.
Visiting the Site Today
The Kobe Site itself remains an open archaeological landscape rather than a developed heritage park. There is no museum building on the ground, and outside of guided visits arranged through the Usa City Board of Education, casual visitors will see fields and traces of earthwork rather than reconstructed buildings.
For a fuller experience, head first to the Oita Prefectural Museum of History at Usa Fudoki-no-Oka, a ten-minute drive from JR Usa Station. The museum sits within the Kawabe-Takamori burial mound park, so a single visit lets you see the pottery excavated from Kobe, the mirrors recovered from Akatsuka Kofun, and the tumulus itself, all within walking distance of one another. The exhibits also cover the wider story of Kyushu's connections to early Yamato Japan and the medieval Buddhist culture of the Kunisaki Peninsula.
- 📍 Plan Your Visit to Oita
- Find tours, activities & transport passes near Obe Ruins
- [ Beppu Hell Tour & Yufuin Onsen Hot Springs ]
Q&A
- When was the Kobe Site occupied?
- The settlement was in use during the Early Kofun period, roughly from the late 3rd century into the 4th century. It went through three clear phases: a moated village, an elite residence inside the moat, and finally a cluster of small square moated tombs.
- Can the public visit the actual excavation site?
- The site is in agricultural land in Araki, Usa City, and is not generally developed for tourism. Visitors interested in the archaeology should contact the Usa City Board of Education in advance, or visit the Oita Prefectural Museum of History where artifacts are on display.
- What was found in the excavations?
- Excavators identified the ditch system with its southern projections, the inner enclosure of wooden posts, the postholes of a large raised-floor building roughly 8 meters by 5.6 meters, and several square moated tombs. Among the small finds, the most significant are pottery vessels imported from the Kinai and Kibi regions across the Inland Sea.
- How is the site related to Akatsuka Kofun?
- Akatsuka Kofun, a 57.5-meter keyhole tumulus dated to the late 3rd century, sits roughly two kilometers from Kobe and was active at the same time as the Kobe residence. Many researchers consider it likely that the chiefly lineage that occupied Kobe was buried at Akatsuka, making the two sites complementary aspects of a single elite community.
- What is the significance of the imported pottery?
- Pottery from the Kinai region (around modern Nara and Osaka) and Kibi (modern Okayama) shows that Kobe was tied into a maritime network running along the Seto Inland Sea. In the 3rd and 4th centuries, that network was the principal route for the political and cultural integration of western Japan under the emerging Yamato polity.
Basic Information
| Name | Kobe Site (小部遺跡, Kobe Iseki) |
|---|---|
| Location | Araki, Usa City, Oita Prefecture |
| Type of Site | Early Kofun-period moated settlement and chief's residence |
| Period | Early Kofun period (late 3rd to 4th century) |
| Designation | National Historic Site (国史跡) |
| Date of Designation | March 26, 2021 (Reiwa 3); additional land added March 10, 2025 (Reiwa 7) |
| Designated Area | 13,508.27 square meters |
| Designation Criterion | Category 1: shell mounds, settlement sites, tumuli and similar archaeological sites |
| Related Museum | Oita Prefectural Museum of History (Kyozuka, Takamori, Usa City). Selected pottery on permanent display. |
| Access | Approximately 15 minutes by car from JR Usa Station; the related museum and Akatsuka Kofun are roughly 10 minutes from the same station. |
| Public Access | The site itself is in farmland with no permanent visitor facilities. Direct visits are best arranged through the Usa City Board of Education, Cultural Properties Section. |
References
- National Designated Cultural Properties Database, Agency for Cultural Affairs — Kobe Site (国指定文化財等データベース)
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/00004120
- Kobe Site Designated as National Historic Site / Usa City (小部遺跡が国指定史跡に指定されました／宇佐市)
- https://www.city.usa.oita.jp/sougo/soshiki/18/shakaikyoiku/3/bunkazai/12565.html
- Oita Prefectural Museum of History (大分県立歴史博物館)
- https://www.pref.oita.jp/site/rekishihakubutsukan/
- Kobe Site 19th Excavation Report / Comprehensive Database of Archaeological Site Reports in Japan (全国遺跡報告総覧)
- https://sitereports.nabunken.go.jp/ja/71522
Last verified: 2026.05.27