Sosha: The Heart of Ancient Kozuke
Sanno Temple Ruins stand on slightly elevated ground between the Yahata River and Ushii River, on the southeastern foothills of Mount Haruna.
The surrounding area contains numerous important archaeological sites, including the Sosha Kofun Group, the Kozuke Provincial Government Ruins, and the Kozuke Kokubunji and Kokubunji Convent Ruins.
Together, these remains reveal that the Sosha area was a major center of ancient Kozuke by the 7th century.
Sanno Temple is believed to have been the clan temple of the Kamitsukeno clan, an influential ancient family with close connections to the Yamato court. The site therefore provides valuable evidence of the political and religious relationships that connected regional elites with the central government.
The Temple Known as Hokkoji
The Temple Name Recorded on the Yamanoue Stone Monument
Archaeological excavations uncovered roof tiles inscribed with characters such as “Hokkoji” and “Hoko.” These discoveries established that Sanno Temple was the same temple known in historical sources as Hokkoji.
The Yamanoue Stone Monument, erected in 681 during the Asuka period, records that a monk named Chori of Hokkoji was involved in its construction. This provides important evidence that the temple was already in existence by the late 7th century.
A later document, the Ueno Province Replacement Register, compiled in 1030, records a request to remove Hokkoji from the list of officially supported temples because it had already fallen into ruin.
Archaeological evidence similarly suggests that the temple remained active from the late 7th century until around the 11th century.
A Sophisticated Temple Layout
Hokiji-Style Temple Plan
The temple precinct was enclosed by a corridor measuring approximately 79.7 meters from east to west and 81 meters from north to south.
The principal buildings were arranged according to a Hokiji-style layout, with the Main Hall to the west, a pagoda to the east, and the Lecture Hall to the north.
This carefully planned arrangement reflects the advanced Buddhist architectural traditions of the period.
The Main Hall measured approximately 22 meters square, while the Lecture Hall measured about 37.8 meters east-west and 24.5 meters north-south. The pagoda platform measured approximately 13.5 meters square.
The Massive Pagoda Foundation Stone
The pagoda’s central foundation stone is particularly impressive. This enormous stone measures approximately 2.5 to 2.7 meters in diameter and about 1.5 meters thick.
A carefully carved circular hole at its center was used for the pagoda’s central pillar and its sacred relic chamber, demonstrating the sophisticated engineering and craftsmanship of the builders.
The Stone Lotus Fitting for the Pagoda’s Central Pillar
One of the most distinctive artifacts from Sanno Temple is the stone fitting surrounding the base of the pagoda’s central pillar.
Made from seven pieces of andesite, the stones were arranged to create the appearance of a large lotus flower. At the center is a circular opening approximately 96.5 centimeters in diameter.
The fitting was designed to decorate and protect the base of the pagoda’s central pillar. Comparisons with archaeological remains in China helped researchers determine its original function.
This remarkable stonework demonstrates the high level of stone-carving technology available in ancient Japan and was designated an Important Cultural Property in 1953.
Remarkable Artifacts from the Excavations
A Rare Stone Shibi Roof Ornament
Another particularly valuable discovery is a stone shibi, a decorative ornament originally placed along the ridge of a temple roof.
Shibi were traditionally associated with protection against fire. In Japan, they were normally made of roof tile, making stone examples exceptionally rare.
Only three examples of stone shibi are known from archaeological sites in Japan, and two of them were discovered at Sanno Temple.
Carved from hornblende andesite and pyroxene andesite, the pieces are estimated to have originally stood more than one meter high.
Their sophisticated forms and craftsmanship have been regarded as comparable to those found at major temples in the Kinai region, the heartland of ancient Japan around present-day Nara and Osaka.
Green-Glazed Pottery and Clay Sculptures
In 1961, researchers discovered green-glazed vessels, bowls, and plates, together with a bronze bowl.
These fine objects date from the early Heian period and reflect the tradition of Nara sancai, a type of three-colored glazed pottery. They are believed to have been used in esoteric Buddhist rituals.
These artifacts were designated Important Cultural Properties in 1966.
More than 4,000 fragments of clay sculptures were also unearthed during excavations. They are thought to have formed a group of clay Buddhist figures originally installed inside the first story of the pagoda.
The sculptures appear to have been gathered and buried after the temple suffered a fire. Their quantity and artistic quality have been compared with the famous clay sculptures inside the five-story pagoda at Horyuji Temple in Nara Prefecture.
Excavation and Preservation
Research at the site began after the accidental discovery of the pagoda’s foundation stone in 1921.
In 1928, the site was designated as a National Historic Site under the name “Sanno Tower Site.” In 2008, the designated area was expanded and the site was renamed “Sanno Temple Ruins.”
Large-scale archaeological excavations were carried out between 1974 and 1981, revealing the remains of the Main Hall, Lecture Hall, and other structures.
Additional investigations have continued in connection with infrastructure and road construction, gradually revealing a clearer picture of the original temple precinct.
Visiting Sanno Temple Ruins
Today, Sanno Temple Ruins have been preserved as a historic site park, where visitors can see archaeological remains such as the pagoda foundation stone at close range.
Standing among the remains, it is possible to imagine the pagoda and Main Hall that once stood here more than 1,300 years ago. The quiet surroundings provide an evocative setting for experiencing the distant world of ancient Buddhism.
Sosha History Museum
Next to the ruins, the Maebashi City Sosha History Museum displays replicas of the stone fitting from the pagoda’s central pillar, the stone shibi, clay sculptures, and excavated roof tiles.
The museum provides additional information about the archaeological discoveries and helps visitors understand what the ancient temple may have looked like.
Exploring the Ancient Sites of Sosha
Sanno Temple Ruins are part of a larger concentration of ancient historical sites in the Sosha area.
Nearby attractions include the Kozuke Kokubunji Temple Ruins, the Kozuke Kokubunji Convent Ruins, and the Sosha Kofun Group. Visiting these sites together offers a broader picture of the development of ancient Kozuke and its connections with the central Japanese government.
As one of the earliest known Buddhist temple sites in the region, Sanno Temple Ruins are an important place for understanding the emergence and development of ancient Kozuke.
A Glimpse of Hakuho Culture in Ancient Gunma
Sanno Temple Ruins preserve valuable evidence of Hakuho-period Buddhist culture in Gunma.
The sophisticated temple layout, exceptional stonework, rare stone roof ornaments, green-glazed pottery, and thousands of clay sculpture fragments reveal the remarkable cultural and religious environment that existed here more than a millennium ago.
For travelers interested in archaeology, Buddhist history, ancient Japanese architecture, and the origins of regional culture, Sanno Temple Ruins offer a fascinating historical experience in Maebashi.
Combining a visit to the ruins with the nearby historical museum and other ancient sites around Sosha makes it possible to explore the landscape of ancient Kozuke and imagine the prayers, craftsmanship, and political connections that shaped this area more than 1,300 years ago.