Five Gold Bells and the Last Great Keyhole Tomb of Eastern Japan
On 31 July 1950, the closing day of an excavation in Kisarazu, diggers reached the floor of an undisturbed stone chamber and lifted out five tiny bells of pure gold. Each stands about one centimetre tall, measures nine millimetres across, and weighs only 1.25 grams, yet their surfaces had kept their shine for some fourteen centuries underground. The find renamed the tomb itself. What people had long called Futagozuka, the "twin mounds," became Kinreizuka, the "Gold Bell Mound."
The bells are the headline pieces of a much larger group of grave goods now registered together as a single national holding: the Kinreizuka Kofun Excavated Objects of Chiba Prefecture. The collection covers swords, horse fittings, mirrors, body armour, beads, bronze vessels and pottery, all recovered from one burial. Most of it is shown at the Kisarazu City Museum of History, whose nickname Kin no Suzu, "the golden bell," comes directly from these five objects. A portion is held at the National Museum of Japanese History in Sakura.
A Tomb Built at the Very End of an Era
Kinreizuka is a zenpokoenfun, a keyhole-shaped mound combining a round rear and a squared front, located in the Nagasuka district of Kisarazu. It belongs to the Gion and Nagasuka tomb cluster, where burial mounds were raised from the early 5th to the mid 7th century. Estimates of its original length run from roughly 90 to 100 metres. Today only part of the round section survives, hemmed in by houses, with the mound now standing around 3.5 metres high where it once rose to about 6.
The grave goods point to construction in the late 6th or early 7th century. That timing matters. By then the keyhole form, which had defined elite burial across the archipelago for three hundred years, was being abandoned almost everywhere. Outside the Kanto region, mounds longer than 100 metres had all but vanished apart from a handful of royal tombs. Kinreizuka was among the largest keyhole mounds of this final generation, and it was built without the rows of haniwa clay figures that had accompanied earlier tombs. It marks, in a real sense, the end of a tradition.
Who was buried here is still debated. The scale of the mound and the wealth of the offerings suggest a paramount chief of the Obitsu River basin. One long-standing view identifies the occupant with the Mumakuta no kuni no miyatsuko, a regional ruler recognised by the early Yamato court, though the question remains open. The stone chamber held more than one burial, so the tomb served a family or lineage rather than a single individual.
Why the Collection Was Designated
The artifacts were designated an Important Cultural Property on 27 June 1959, with further objects added to the listing on 30 September 2020. Two qualities set the group apart. The first is its completeness: because the chamber had never been robbed, archaeologists recovered an unusually full picture of how a high-ranking person of the late Kofun period was equipped for the afterlife. The second is the quality of the metalwork.
The decorated swords are the clearest example. The burial yielded close to twenty ornamental long swords of several distinct types, a range of forms rarely matched at any single site in Japan. Among them are gilt-bronze swords with ring-shaped pommels, including examples carved with a confronting pair of dragons, alongside swords with knob-shaped and capped hilt ends. Gilt-bronze saddle fittings, harness ornaments, horse bells, two bronze mirrors, an iron helmet, scales from a suit of lamellar armour, lidded bronze bowls on stands, and beads of agate, rock crystal, amber and glass round out the assemblage. Taken together, the objects show how thoroughly material culture in eastern Japan was tied into the networks of the Yamato court.
What to Look For at the Museum
The five gold bells have their own dedicated display room, and seeing them in person tends to surprise visitors. Photographs make them look substantial; in the case they are smaller than a fingertip, which is part of their appeal. Look closely at the casting and the suspension loop on each bell.
The decorated swords reward slow viewing. Rather than passing along the row, it is worth comparing the pommels: the paired dragons of the ring-pommel type, the rounded knob of another, the way gilt and silver were used to mark rank and status. The horse fittings tell their own story about the importance of cavalry and display among the regional elite. The museum sets the Kinreizuka material within the wider history of Kisarazu, so the gold and gilt-bronze pieces sit alongside displays on later salt and seaweed industries and on local well-digging techniques, giving a sense of how one place changed across many centuries.
Around the Museum
The museum sits inside Otayama Park, on a hill east of Kisarazu Station, a spot known for cherry blossom in spring. A short walk away stands the Kimisarazu Tower, a viewpoint tied to the legend of the hero Yamato Takeru and his consort Ototachibana-hime; local tradition links the very name Kisarazu to that story. Within the same park you can also visit the former Anzai Residence, a preserved traditional farmhouse designated by the city.
The actual tomb lies a little distance away in the Nagasuka neighbourhood, where only a fragment of the mound remains among the houses, so the museum, not the site, is where the discovery comes alive. Kisarazu is easy to reach from Tokyo across the Aqua-Line, which makes the collection a feasible half-day trip for travellers based in the capital.
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Q&A
- Where can I see the gold bells and the rest of the collection?
- Most of the material, including the five gold bells, is on display at the Kisarazu City Museum of History (Kin no Suzu) in Otayama Park. A portion is held by the National Museum of Japanese History in Sakura, Chiba. Items there may rotate, so check current displays before a special trip.
- How much does it cost to visit?
- Admission to the permanent exhibition at the Kisarazu museum became free for all visitors from fiscal 2024. Special exhibitions may carry a separate charge of up to 1,000 yen. The museum is open 9:00 to 17:00, with last entry at 16:30, and is closed on Mondays and over the New Year period.
- How old are the bells, and why are they significant?
- They date to the late 6th or early 7th century, roughly 1,400 years ago. Pure gold bells of this kind are exceptionally rare in Japanese tombs, and the fact that the whole burial survived untouched makes the group an important record of late Kofun-period elite culture.
- Can I visit the Kinreizuka tomb itself?
- Only a part of the round mound remains, set within a residential area of Nagasuka, and there is little to see compared with the museum displays. Most visitors focus on the museum, where the excavated objects and their story are presented in full.
- How do I get to Kisarazu from Tokyo?
- Kisarazu is reached by JR train via the Uchibo Line, or by highway bus across the Tokyo Bay Aqua-Line, which is fast and direct. From Kisarazu Station, the museum is about a 20-minute walk uphill from the east exit.
Basic Information
| Name | Kinreizuka Kofun Excavated Objects of Chiba Prefecture |
|---|---|
| Category | Archaeological materials (Important Cultural Property) |
| Designation | Important Cultural Property, designated 27 June 1959; objects added 30 September 2020 |
| Quantity | One collective lot (swords, horse fittings, mirrors, armour, beads, bronze vessels, pottery and more) |
| Period | Kofun period, late 6th to early 7th century |
| Owner | Kisarazu City |
| Where held | Kisarazu City Museum of History (Kin no Suzu), 2-16-2 Ota, Kisarazu, Chiba; part at the National Museum of Japanese History, 117 Jonai-cho, Sakura, Chiba |
| Hours | 9:00 to 17:00 (last entry 16:30); closed Mondays and 28 December to 4 January |
| Admission | Permanent exhibition free (from fiscal 2024); special exhibitions up to 1,000 yen |
| Access | About 20 minutes on foot from the east exit of JR Kisarazu Station; roughly 15 minutes by car from the Sodegaura interchange on the Tokyo Bay Aqua-Line |
References
- National Database of Designated Cultural Properties, Agency for Cultural Affairs
- https://kunishitei.bunka.go.jp/bsys/maindetails/201/9796
- Cultural Heritage Online, Agency for Cultural Affairs
- https://online.bunka.go.jp/heritages/detail/201953
- Kisarazu City Museum of History Kin no Suzu (official site)
- https://www.city.kisarazu.lg.jp/soshiki/kyoikuiinkai/kyodohakubutsukankinnosuzu/1/2742.html
- Kinreizuka Kofun, Chiba Prefectural Government
- https://www.pref.chiba.lg.jp/kyouiku/bunkazai/bunkazai/p411-014.html
Last verified: 2026.06.20