Sukumozuka Kofun is a nationally designated historic site in Kushiro-cho, Masuda City, Shimane Prefecture. This impressive ancient burial mound offers a fascinating glimpse into the history of early Japan and the powerful local leaders who shaped the region more than 1,500 years ago.
Since its discovery in 1939, the kofun has been the subject of archaeological research and investigation. Its size and unusual structure have gradually become clearer, and it is now recognized as one of the largest burial mounds in Shimane Prefecture.
Sukumozuka Kofun was first discovered by a local historian. A full-scale archaeological excavation was carried out in 1941.
At first, researchers believed that the site was a large circular burial mound. As surveying techniques and archaeological research progressed, however, the possibility that it was actually a keyhole-shaped burial mound became increasingly likely.
In 2022, this interpretation was officially confirmed. The discovery significantly increased the archaeological importance of Sukumozuka Kofun, suggesting that it was the burial place of a powerful local leader who played an important political and cultural role in ancient Masuda.
Sukumozuka Kofun has a total length of approximately 96 meters. The rear circular section measures about 56 meters in diameter and rises approximately 7 meters high.
The front section extends for approximately 40 meters, creating the distinctive keyhole shape characteristic of many large kofun built during ancient Japan’s Kofun period.
The scale of the monument is remarkable when considered in the context of the technology available at the time. Constructing such a large mound would have required considerable labor, organization, and technical expertise, indicating the presence of a powerful political authority in the region.
One of the most distinctive features of Sukumozuka Kofun is the square platform known as a hōkeidan built on the front section of the mound.
This type of structure is relatively unusual among Japanese burial mounds and provides important clues about the construction techniques and ceremonial practices of the period.
The surface of the kofun was covered with fukiishi, rounded stones carefully arranged over the mound. The orderly placement of these stones demonstrates the advanced construction techniques used by the people who built the monument.
For modern visitors, the surviving traces of these features provide a tangible connection to the engineering and craftsmanship of ancient Japan.
Archaeological research has also confirmed that haniwa were placed on top of the burial mound. These included cylindrical haniwa as well as shōgai-shaped haniwa, which resemble flowering morning-glory blossoms.
Haniwa were not simply decorative objects. Their placement around elite burial mounds is believed to have played important ceremonial and symbolic roles. Their presence at Sukumozuka Kofun shows that the site was designed as a powerful representation of status and authority.
Based on the characteristics of the excavated haniwa, Sukumozuka Kofun is believed to have been constructed during the late 4th century, around the transition from the latter part of the Early Kofun period to the beginning of the Middle Kofun period.
This was a major period of political change in Japan. Large burial mounds were being constructed in various parts of the country, reflecting the growing power of regional elites and the development of increasingly organized political communities.
Sukumozuka Kofun is thought to have been built as the tomb of a powerful local leader. Its size and design suggest that the Masuda area was already an important regional center during ancient times.
The name “Sukumozuka” is traditionally said to come from a story that the mound was formed from piles of unwanted rice husks, known in Japanese as momi-gara.
Although this is a local legend rather than an archaeological explanation for the mound’s construction, such stories are an important part of the cultural history surrounding ancient monuments. They show how the site continued to be recognized and remembered by local communities long after its original purpose had been forgotten.
Sukumozuka Kofun stands in a hilly area on the eastern side of the Masuda Plain. The site is surrounded by greenery and offers a peaceful setting for exploring ancient history.
The mound was once covered by dense woodland, making its overall shape difficult to recognize. Local efforts to maintain and restore the site have opened up the area, allowing visitors to appreciate the distinctive form of the ancient burial mound more clearly.
A pond on the western side of the kofun has been planted with ancient lotus flowers. From late June through early August, the pond is decorated with beautiful pink blossoms.
The combination of the ancient burial mound, seasonal flowers, and surrounding greenery creates a particularly atmospheric setting. Visitors can take a leisurely walk while imagining the landscape of the distant past.
Every April, the area hosts the Sukumozuka Kofun Festival. The event features traditional kagura performances and presentations by local residents.
The festival brings the archaeological heritage of the kofun together with living local culture, offering visitors an opportunity to experience Masuda’s history in a more lively and contemporary setting.
Sukumozuka Kofun can be reached in approximately 15 minutes by bus from Masuda Station, making it a relatively easy destination to include in a sightseeing itinerary around Masuda.
There is no need to hurry when visiting the site. Take time to walk around the mound, observe its shape and surrounding landscape, and imagine the enormous effort required to construct such a monument more than 1,500 years ago.
Sukumozuka Kofun is one of the most fascinating ancient monuments in the San’in region. Its impressive scale, unusual structure, haniwa, and stone-covered mound provide valuable clues about the technology, beliefs, and social organization of ancient Japan.
The discovery that the site is a keyhole-shaped kofun, officially confirmed in 2022, has further highlighted its significance as an archaeological site.
For travelers interested in Japanese history, archaeology, ancient culture, or simply peaceful places away from the major tourist routes, Sukumozuka Kofun offers a memorable opportunity to encounter the distant past.
Standing beside the enormous mound, it is easy to imagine the powerful leader who may have been buried here and the community that gathered to construct this extraordinary monument.
With its combination of ancient history, archaeological discoveries, local legends, seasonal flowers, and community traditions, Sukumozuka Kofun provides a unique perspective on the history of Masuda.
When exploring western Shimane, consider adding this remarkable kofun to your itinerary and take a moment to experience the scale and atmosphere of ancient Japan.