358 Bronze Swords on a Hillside in Izumo
In the summer of 1984, a survey ahead of farm-road construction cut into a south-east-facing slope at Kanba, in what is now Izumo City, Shimane Prefecture. The trench exposed something no one expected: row upon row of bronze swords, blades set upright, packed into the earth. When the soil was cleared, the count reached 358. A few meters to the west lay a second pit holding 16 bronze spearheads and 6 bronze bells. Full excavation followed in 1985.
This single find, recovered from the Kōjindani site, more than doubled the number of Yayoi-period bronze swords that had been excavated across the whole of Japan up to that point. The assemblage of 358 swords, 16 spearheads, and 6 bells is now collectively designated a National Treasure and is normally held by the Shimane Museum of Ancient Izumo, next to the great shrine of Izumo Taisha.
The Yayoi period (roughly the last few centuries BCE through the third century CE) was the era when wet-rice farming and bronze and iron metallurgy spread across the Japanese archipelago. Bronze swords, spearheads, and bells of this kind were not battlefield gear or instruments in any everyday sense. By the time they were buried, they had become ritual objects, cast to be offered, displayed, or interred rather than carried.
Why the Find Rewrote the Map
Before Kōjindani, scholars often described Yayoi bronze culture as splitting into two broad zones: a bell-using region centered on the Kinai plain around present-day Nara and Osaka, and a weapon-using region centered on northern Kyushu. Izumo, on the Japan Sea coast between them, was treated as a margin. Then a single hillside produced all three forms at once, swords concentrated in a shape distinctive to the Izumo area, bells of a type tied to the Kinai sphere, and broad spearheads of a type tied to northern Kyushu.
That mixture, recovered through a controlled archaeological dig rather than chance disturbance, is what gives the cache its weight. It suggested that Izumo was not a backwater but a place where these separate ritual traditions met. The discovery prompted a wholesale rethinking of how bronze moved and meant something in late prehistoric western Japan. The point was reinforced in 1996, when 39 bronze bells came out of the Kamoiwakura site only a few kilometers away, another National Treasure that places Izumo near the center of the story rather than its edge.
The objects were designated an Important Cultural Property on June 6, 1985, soon after excavation, and elevated to National Treasure status on June 30, 1998. The owner of record is the national government, through the Agency for Cultural Affairs.
What to Look For Up Close
The swords reward slow attention. All 358 belong to a single narrow-blade type and run about 51 centimeters long. They had been laid out in four west-to-east rows of 34, 111, 120, and 93, each blade standing upright. Closer study turned up two telling details. Some blades had never received their final edge-polishing after casting, and large numbers were "same-mold" swords, cast in identical sets from shared molds. Both clues point to intensive production within a short window, around the end of the Middle Yayoi and the start of the Late Yayoi.
The 16 spearheads divide into 2 narrow-form and 14 broader-form pieces. On four of them, the surface carries a technique called differentiated polishing, in which the bronze was burnished a second time at a shifted angle after the usual finish. Catch the light and a faint herringbone pattern rises out of the metal. The same effect appears on spearheads from sites in Saga Prefecture in northern Kyushu, a thread linking the Izumo cache to the wider weapon-bronze tradition.
The 6 bells, each about 22 centimeters tall, had been set in two rows of three with their suspension loops facing inward and their flanges standing upright. One is the oldest type present, decorated with horizontal bands, while the other five belong to a slightly later stage carrying the cross-sash design that runs in dividing bands across the body. Seeing the weapons and bells side by side makes the cache's central puzzle physical: why bury traditions from opposite ends of the archipelago together, in one slope, with such evident care?
Visiting the Site and Seeing the Bronzes
A word of planning first. The Shimane Museum of Ancient Izumo, the National Treasure's usual home, is closed for seismic retrofitting and is scheduled to reopen around October 2026. While it is shut, the place to go is the find spot itself.
The Kōjindani Museum sits beside the original excavation in the Saidani valley at Kanba, Hikawa, in Izumo City. It is a site museum built to let visitors stand where the bronze came out of the ground. Displays explain the discovery and the objects in depth, with replica swords, spearheads, and bells; the actual National Treasure pieces are shown only during limited special periods, so check ahead if seeing the originals matters to you. A short walk away, the excavation point has been reconstructed with replicas arranged as the bronzes were found, viewable from a slight rise that takes in the whole slope.
The surrounding Kōjindani Historic Site Park, open since 1995, makes a relaxed half-day. In mid-June, the paddy in front of the museum fills with some 50,000 ancient lotus blossoms, a strain known as Ōga lotus, which draws visitors of its own. The museum is open 9:00 to 17:00 with last entry at 16:30, closed Tuesdays and over the New Year holidays, and admission to the exhibition room is modest. Reaching it is easiest by car, about five minutes from the Hikawa interchange on the San-in Expressway or roughly ten minutes from Izumo Airport; the nearest station, Shōbara on the JR San-in Line, is about a 40-minute walk or a short taxi ride. Pair the visit with Izumo Taisha and the museum district nearby once the larger museum reopens.
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Q&A
- Can I see the actual National Treasure bronzes right now?
- The originals are normally displayed at the Shimane Museum of Ancient Izumo, which is closed for renovation until around October 2026. During the closure, the nearby Kōjindani Museum shows high-quality replicas year-round and the genuine bronzes only during limited special exhibitions, so confirm the schedule before traveling if you want to see the originals.
- Why were so many bronze objects buried together?
- The exact reason is not known. The careful arrangement and the deliberate burial point to ritual rather than storage or hoarding, but who buried them, and why they combined sword, spear, and bell traditions from different regions, remain open questions that researchers continue to debate.
- How does Kōjindani connect to Izumo's famous mythology?
- Izumo looms large in Japan's oldest chronicles and is the setting for many early myths. The Kōjindani bronzes give material evidence that the region held real ritual and political importance in the Yayoi period, lending archaeological depth to a place better known through legend.
- How long should I allow for a visit?
- About an hour covers the museum and the reconstructed excavation point together, roughly 30 minutes each. Allow longer in mid-June if you want to walk among the lotus blooms or explore the wider historic park.
Basic Information
| Name | Bronze Artifacts Excavated from the Kōjindani Site, Shimane Prefecture |
|---|---|
| Category | Archaeological materials (National Treasure) |
| Components | Bronze swords (358), bronze spearheads (16), bronze bells (6); designated collectively |
| Period | Yayoi (swords dated to the end of the Middle Yayoi and start of the Late Yayoi) |
| Designations | Important Cultural Property, June 6, 1985; National Treasure, June 30, 1998 |
| Owner | National government (Agency for Cultural Affairs) |
| Holding institution | Shimane Museum of Ancient Izumo (closed for renovation until around October 2026) |
| Find site | Kōjindani site, Kanba, Hikawa, Izumo City, Shimane Prefecture |
| Where to visit | Kōjindani Museum and Historic Site Park, beside the excavation (open 9:00–17:00, closed Tuesdays) |
References
- National Database of Designated Cultural Properties, Agency for Cultural Affairs
- https://kunishitei.bunka.go.jp/bsys/maindetails/201/10024
- Kōjindani Museum (official site)
- https://www.kojindani.jp/
- Shimane Museum of Ancient Izumo (official site)
- https://www.izm.ed.jp/
- Shimane Tourism Navigation, Shimane Prefecture Tourism Federation
- https://www.kankou-shimane.com/destination/20313
Last verified: 2026.06.12