Tawayama and Kamagota Ruins

Tawayama and Jingoda Sites: A Mysterious Yayoi-Period Triple-Moat Settlement in Matsue

Perched atop an isolated hill overlooking the shimmering waters of Lake Shinji, the Tawayama and Jingoda Archaeological Sites (田和山・神後田遺跡) in Matsue City, Shimane Prefecture, present one of Japan's most enigmatic ancient mysteries. This nationally designated Historic Site preserves the remains of a Yayoi-period settlement dating from approximately the 4th to the 1st century BC, distinguished by an extraordinary triple-moat system that has puzzled archaeologists since its discovery in the late 1990s.

What makes Tawayama truly remarkable is not merely its impressive scale, but rather what is absent from its core: despite being encircled by three concentric moats carved deep into the hillside, the summit contained no residential dwellings whatsoever. Only two small post-built structures stood within the moated enclosure, while all houses were located on the slopes outside the moats. This unprecedented layout, found nowhere else in Japan, has inspired theories ranging from a mountaintop fortress to a sacred ritual sanctuary, making Tawayama one of the most debated archaeological sites in the country.

Historical Background and Discovery

The Tawayama site was excavated between 1997 and 2000, prompted by plans to construct the Matsue Municipal Hospital on the hilltop. The excavation was carried out by the Matsue City Board of Education and yielded such significant finds that the hospital construction plans were altered to preserve the archaeological remains in their original location.

The site occupies an independent hilltop rising 45 meters above sea level, with a relative height difference of 36 meters from the surrounding terrain. It overlooks Lake Shinji to the north and offers panoramic views of the Shimane Peninsula, Matsue cityscape, Mount Chaususan, and even the distant Mount Daisen on clear days.

In 2001, Tawayama was designated as a National Historic Site. Two decades later, in March 2022, the neighboring Jingoda site — located approximately 500 meters to the north on a low hill — was added to the designation. Both sites share the notable characteristic of having moats that first appeared during the late Early Yayoi period, suggesting an organic relationship between the two settlements. The combined designation is now officially known as the "Tawayama and Jingoda Sites."

Why This Site Was Designated as a National Historic Site

The Tawayama and Jingoda Sites received national designation for several compelling reasons that set them apart from all other known Yayoi-period settlements in Japan.

The most striking feature is the unprecedented structure of the triple-moat enclosure. Typical Yayoi-period moated settlements place dwellings, storage pits, or other domestic structures inside the protective moats. At Tawayama, however, the narrow hilltop area enclosed by the innermost moat — measuring only about 2,250 square meters — contained just post-hole clusters indicating two structures: a five-post building and a nine-post building. All residential dwellings, numbering over 20 from the Yayoi through Kofun periods, were found exclusively outside the moats.

This layout challenges conventional understanding of moated settlements as purely defensive structures and suggests that the hilltop enclosure may have served a ritual or ceremonial purpose. The enormous labor invested in excavating three concentric moats — the largest reaching 7 meters in width and 1.8 meters in depth — around a space that housed no residents raises profound questions about the social organization and beliefs of the community that built them.

Additionally, among the excavated artifacts, a stone slab identified as a possible inkstone (suzuri) from the Chinese Lelang Commandery on the Korean Peninsula stands out as evidence of East Asian exchange networks during the Yayoi period. This artifact, along with stone arrowheads, stone swords, ring-shaped stone axes, and approximately 3,000 throwing stones recovered from the moat floors, was designated as a Shimane Prefecture Cultural Property (Archaeological Material) in 2019.

Highlights and What to See

The Hilltop Enclosure (Summit Zone)

The summit of Tawayama has been carefully restored to show the locations of the ancient fence posts that once encircled the hilltop, as well as the positions of the five-post and nine-post building foundations. Standing markers indicate where these mysterious structures once stood. From this vantage point, visitors are rewarded with a breathtaking 360-degree panorama encompassing Lake Shinji, the Shimane Peninsula, and the surrounding cityscape of Matsue.

The Triple-Moat Zone

Visitors can walk through the area where the three concentric moats were carved into the hillside. During the Early Yayoi period, a single moat with three gaps encircled the summit. By the Middle Yayoi period, this had expanded into the triple-moat configuration visible today. The moats and traces of earthen ramparts between them offer a tangible sense of the monumental effort required to create this enigmatic fortification.

Reconstructed Dwellings

On the northern and western slopes, visitors can explore reconstructed buildings based on archaeological evidence. A pit dwelling (tateana jūkyo) has been faithfully reconstructed on the northern slope, where the remains of over 20 dwellings from the Yayoi to Kofun periods were discovered. On the western slope, both a pit dwelling and a raised-floor storehouse (hottate-bashira tatemono) have been reconstructed. The thatched-roof raised-floor building was renovated in December 2025 as part of the ongoing park improvement project and offers an impressive sight.

Nature Learning Forest

The park's forested areas serve as a natural learning zone, where over 100 species of plants and animals can be observed along observation paths. The combination of archaeological heritage and natural environment creates a uniquely immersive experience, blending history with the beauty of the San'in region's landscapes.

The Jingoda Site

Located about 500 meters north of Tawayama on a low hilltop, the Jingoda site was discovered during development work and revealed a Yayoi-period settlement with pit dwellings and moat traces. The moats at Jingoda also date to the late Early Yayoi period, the same era as the earliest moat at Tawayama. This chronological overlap strongly suggests that the two communities were closely connected, perhaps functioning as complementary parts of a larger settlement network.

The addition of Jingoda to the national designation in 2022 broadened scholarly understanding of the Yayoi-period landscape in the southern Matsue region and its role in the emergence of the Izumo area as a center of ancient culture.

Surrounding Area and Nearby Attractions

Matsue City, the capital of Shimane Prefecture, is one of Japan's most culturally rich cities, renowned for its castle, samurai heritage, and connections to ancient Izumo mythology. Visitors to the Tawayama and Jingoda Sites can easily combine their trip with several other notable destinations.

• Matsue Castle (approximately 3 km north): One of only twelve original castles remaining in Japan and a National Treasure, this imposing fortress offers another perspective on the region's defensive architecture through the ages.
• Matsue History Museum (approximately 3 km north): Located next to Matsue Castle, this museum has hosted special exhibitions on the Tawayama and Jingoda sites and provides excellent context for understanding the region's archaeological heritage.
• Yamashiro Futago-zuka Kofun (approximately 5 km east): The largest burial mound in Shimane Prefecture, dating to the Kofun period, illustrating the continuation of political power in the area after the Yayoi period.
• Izumo Taisha Grand Shrine (approximately 35 km west): One of the oldest and most important Shinto shrines in Japan, deeply connected to Japanese mythology and the Izumo cultural sphere to which Tawayama belonged.
• Lake Shinji Sunset Viewing: The Tawayama hilltop itself is considered one of the finest spots to watch the sunset over Lake Shinji, a celebrated natural spectacle in the San'in region.