Kojindani Ruins is an important archaeological site from Japan’s Yayoi period, located in Kamba, Hikawa Town, Izumo City, Shimane Prefecture. Designated as a National Historic Site, it is famous for the remarkable discovery of hundreds of ancient bronze artifacts. All of the bronze objects excavated here have been collectively designated as National Treasures.
The site first attracted national attention in 1984, when archaeological excavations associated with the construction of a farm road uncovered an extraordinary number of Yayoi-period bronze weapons. The discovery of 358 bronze swords in a single location caused a major sensation in Japanese archaeology.
The findings helped transform the understanding of ancient Izumo. Rather than being known only as a legendary land described in Japanese mythology, Izumo increasingly came to be recognized as an important center of ancient culture and society supported by archaeological evidence.
The most remarkable feature of the Kojindani Ruins is the sheer number and variety of bronze artifacts discovered here. In 1984, archaeologists uncovered 358 bronze swords buried together in the soil on a hillside. At the time, only around 300 bronze swords had been discovered in total across Japan, making this single discovery unprecedented.
The following year, in 1985, another burial pit was discovered about seven meters from the bronze swords. It contained six bronze bells and 16 bronze spearheads.
The simultaneous discovery of bronze bells and bronze spearheads at the same site was unprecedented, while the presence of three major types of Yayoi bronze objects—swords, bells, and spearheads—provided exceptionally valuable evidence for understanding the culture and society of ancient Japan.
The 358 bronze swords are remarkably uniform in size and shape. Most are approximately 50 centimeters long and weigh around 500 grams.
They had been carefully arranged in four rows and buried upright with their blades standing vertically beneath a constructed terrace on the hillside. The orderly arrangement suggests that the swords were deliberately placed rather than simply discarded.
Although the exact purpose of the swords remains unknown, their careful arrangement provides important clues for researchers studying Yayoi-period rituals, beliefs, and social organization.
About one year after the discovery of the swords, magnetic surveying revealed another burial pit. Excavations uncovered six bronze bells and 16 bronze spearheads.
Bronze bells, known as dotaku, are distinctive ritual objects associated with the Yayoi period. Bronze spearheads, on the other hand, have characteristics associated particularly with northern Kyushu and are generally regarded as having a weapon-related function.
The fact that bronze bells commonly associated with western Honshu and spearheads with strong connections to northern Kyushu were buried together at Kojindani suggests that ancient Izumo may have maintained wide-ranging cultural connections with different parts of Japan.
The discovery began in 1983 during an archaeological survey conducted in connection with the construction of the Izumo Roman Kaido regional farm road.
One of the surveyors noticed fragments of pottery from the Kofun period in a rice-field embankment. This small discovery led to further investigation and eventually to the major excavation that began the following year.
The name Kojindani comes from a nearby shrine dedicated to Sanpo Kojin, a traditional deity worshipped in the southern part of the valley.
One of the intriguing mysteries of the Kojindani bronze swords is the presence of markings on their surfaces. Of the 358 swords, 344 bear an “X” mark.
The meaning of these marks remains uncertain. They are thought to have been carved into the swords with a tool after the objects had been cast, but their purpose has not been definitively established.
Another fascinating connection can be found at the nearby Kamo Iwakura Ruins, approximately three kilometers away. A number of bronze bells discovered there also bear similar marks, suggesting that the two archaeological sites may have been connected in some way.
One of the greatest mysteries surrounding the Kojindani Ruins is why such a large collection of valuable bronze objects was deliberately buried. No definitive explanation has yet been established, and several theories have been proposed.
One theory is that the bronze objects were buried as part of agricultural rituals, perhaps prayers for abundant harvests or rainfall. Bronze objects may have played an important role in ceremonies intended to communicate with supernatural powers.
Another possibility is that the objects were buried for safekeeping and brought out when they were needed for ceremonies.
Some researchers have suggested that the valuable bronze objects may have been hidden to protect them from rival groups or during periods of conflict.
Another interpretation is that the objects had fallen out of use as society changed and were deliberately buried as part of a ritualized form of disposal.
None of these theories has been conclusively proven. This unresolved mystery is one of the reasons the Kojindani Ruins continue to fascinate archaeologists and visitors alike.
Today, the area surrounding the archaeological site has been preserved as Kojindani Historic Park. Covering approximately 27.5 hectares, the spacious park combines archaeological preservation with opportunities for recreation, education, and experiencing nature.
The park was developed as a historic site park in 1995 and has become a popular destination for visitors interested in ancient Japanese history.
Visitors can see the actual location where the 358 bronze swords were discovered. Replicas recreate the original arrangement, allowing visitors to visualize how the swords were carefully placed in the hillside.
For anyone interested in Japanese archaeology, seeing the reconstructed burial site offers a fascinating opportunity to connect the archaeological discoveries with the landscape where they were originally made.
The park also features a reconstructed pit dwelling representing everyday life during the Yayoi period. The structure helps visitors imagine how people lived approximately 2,000 years ago.
It is particularly suitable for families and students, offering an accessible way to learn about ancient Japanese lifestyles while exploring the surrounding natural environment.
Ancient varieties of rice, including black rice and red rice, are cultivated in rice paddies within the park. Seasonal events sometimes allow visitors to experience activities such as rice planting and harvesting.
These hands-on experiences provide a unique opportunity to learn about the agricultural traditions that supported communities during the Yayoi period.
Around June, the park becomes especially beautiful when approximately 50,000 ancient lotus flowers, known as Oga lotus, bloom across the grounds.
The combination of archaeological remains, reconstructed ancient buildings, and seasonal flowers makes Kojindani Historic Park a memorable place to experience both the history and natural beauty of Izumo.
Located within the historic park, the Kojindani Museum introduces the history of the ruins and the remarkable archaeological discoveries made here.
Large-screen presentations, dioramas, panels, and other displays explain the excavation and the bronze artifacts in an easy-to-understand way, making the museum enjoyable even for visitors with no previous knowledge of Japanese archaeology.
In July, the month associated with the discovery of the bronze artifacts, some of the actual National Treasure objects may be displayed at the site as part of a special “homecoming exhibition.” Seeing the original treasures near the place where they were unearthed is a particularly rare and memorable experience.
The Kojindani Ruins are an essential destination for anyone interested in the ancient history of Japan. The extraordinary collection of bronze swords, bells, and spearheads provides valuable clues about the culture, rituals, technology, and regional connections of the Yayoi period.
The discoveries also changed the way ancient Izumo is understood. Archaeology has revealed a society that was connected to a much wider world, adding an important historical dimension to a region long celebrated in Japanese mythology.
Today, the site is more than an archaeological landmark. With its expansive historic park, museum, reconstructed dwelling, ancient rice fields, and seasonal lotus flowers, it offers visitors a chance to explore the landscape and imagine life in Japan approximately 2,000 years ago.
For travelers exploring Izumo, a visit to the Kojindani Ruins is an opportunity to step beyond the famous myths and discover the archaeological evidence that reveals another fascinating side of ancient Japan.