A Monumental Mound Approximately 129 Meters Long
The original burial mound had a total length of approximately 129 meters. The rounded rear section measured about 75 meters in diameter and 9 meters high, while the front section was approximately 68 meters wide and 7 meters high.
The mound was constructed in three tiers and was surrounded by a moat. Carefully arranged fukiishi, or stones covering the surface of ancient burial mounds, were placed on the middle and lower terraces and along the slopes.
When newly constructed, these pale stones would have reflected sunlight, creating an impressive monument that visibly expressed the authority of the person buried within.
Rows of red-painted jar-shaped pottery were also discovered near the top of the mound. These vessels are believed to have been used for rituals before cylindrical haniwa became widespread, providing valuable evidence of ceremonial practices on early burial mounds.
Why Maebashi Tenjinyama Kofun Is Considered One of the Oldest in Eastern Japan
Maebashi Tenjinyama Kofun is regarded as one of the earliest known keyhole-shaped burial mounds in eastern Japan. Several characteristics support this early dating.
1. A Front Section Lower than the Rear Section
Early Kofun-period burial mounds often have a front section that is noticeably lower than the rounded rear section. Maebashi Tenjinyama Kofun retains this characteristic, reflecting an early stage in the development of the keyhole-shaped tomb.
2. Ritual Pottery Predating Haniwa
The red-painted jar-shaped vessels arranged on the summit are believed to represent an early form of funerary ritual that predates the widespread use of haniwa, the clay figures and cylinders commonly associated with Kofun-period tombs.
The pottery provides important evidence supporting a construction date as early as the first half of the 4th century.
3. An Early Burial Facility and Ancient-Style Grave Goods
At the center of the rear mound, archaeologists discovered a nenkaku, a burial facility in which a wooden coffin was enclosed within a thick layer of clay.
The structure measures approximately 7.8 meters long and 1.4 meters wide and is characteristic of burial practices from the early Kofun period.
The grave goods discovered inside also display many features associated with the earliest generations of large Kofun-period tombs.
Excavation and the Effort to Preserve the Tomb
The history of the site’s preservation is particularly remarkable.
In 1968, an archaeological investigation was conducted just before the mound was scheduled to be removed as part of a housing development project. At that time, much of the front section had already been destroyed, and the remaining rear section was also scheduled to be leveled after the investigation.
The first excavation failed to locate the main burial facility, and the ancient tomb appeared to be on the verge of disappearing completely.
However, one of the high school students who had participated in the excavation continued visiting the site after the investigation. While examining a cut section of the damaged mound, the student noticed a mass of clay.
This discovery led to the identification of the previously overlooked clay burial chamber. The development work was halted, and a second investigation was carried out the following year.
Once the burial facility was confirmed and the archaeological importance of the tomb became clear, efforts were made to preserve the central burial area. The episode has since become a memorable example of how individual interest and persistence contributed to the protection of an important cultural heritage site.
Rich Burial Goods Designated as Important Cultural Properties
One of the greatest features of Maebashi Tenjinyama Kofun is the remarkable quality and variety of its burial goods.
A total of 165 objects representing 15 categories were recovered from the clay burial chamber. They included five bronze mirrors, weapons, armor-related objects, tools, beads, and other artifacts.
Together, these discoveries provide valuable evidence of the culture and social structure of early Kofun-period eastern Japan.
Bronze Mirrors and Connections with the Kinai Region
Five bronze mirrors were discovered, including two Sankakubuchi Shinjūkyō, or triangular-rimmed mirrors decorated with figures of deities and mythical animals.
These distinctive mirrors have a triangular cross-section around their rims and images of supernatural beings and animals on their backs. They are particularly associated with western Japan, especially the Kinai region, the political heartland of ancient Japan around present-day Nara and Osaka.
They are also frequently discussed in connection with the famous mirrors traditionally said to have been presented to Queen Himiko of Yamatai from China, although the precise historical relationship remains a subject of scholarly discussion.
Because such mirrors are comparatively uncommon in eastern Japan, their discovery at Maebashi Tenjinyama Kofun suggests that the ancient leaders of this region already had significant connections with the political and cultural networks of central Japan.
Other mirrors include varieties known as Shinsenkyō, Kinju-kyō, and Nejimon-kyō, some of which feature relatively rare decorative designs.
In particular, the Sankakubuchi Goshin Shijūkyō has been suggested to have been cast using the same mold as a mirror discovered at a famous ancient tomb in Nara Prefecture, further highlighting the site’s possible connections with the Kinai region.
Weapons and Tools Reflecting the Authority of the Buried Leader
The burial goods included numerous weapons such as straight swords with ring-shaped pommels, iron swords, iron and bronze arrowheads, as well as various iron tools.
Among the tools were iron axes, iron chisels, and iron adzes. Iron objects were still valuable and relatively uncommon during this period, so their presence in such quantity is significant.
Other finds included a spindle whorl made of jasper and a jar-shaped vessel containing red pigment. These objects suggest that the burial goods represented more than military power alone; they also had ceremonial and symbolic significance.
The collection therefore provides important clues about the technological capabilities, military strength, social hierarchy, and ritual practices of the community that produced the tomb.
The complete collection was designated in 1979 as an Important Cultural Property of Japan under the name “Objects Excavated from Ueno Maebashi Tenjinyama Kofun.” The artifacts are preserved and displayed by the Tokyo National Museum.
The Tomb Today
Much of the original mound was unfortunately removed during the development of the surrounding housing area. Today, only the central area containing the burial facility remains, forming a roughly square elevated section approximately 9 meters high.
The surviving remains no longer convey the full scale of the original 129-meter-long monument. Nevertheless, the site itself tells an important story about the efforts made to protect the central burial structure even as the surrounding landscape was being developed.
Today, the historic site stands quietly among residential neighborhoods. Although the original shape can no longer be fully appreciated, information panels help visitors visualize the enormous mound that once stood here.
What to See When Visiting
Maebashi Tenjinyama Kofun is not a reconstructed burial mound with an elaborate visitor facility. Its appeal lies instead in its archaeological history and the remarkable story of its excavation and preservation.
Understanding how the burial chamber was discovered and learning about the extraordinary collection of grave goods makes the surviving site much more meaningful.
When the artifacts are on display at the Tokyo National Museum, visiting both the museum and the archaeological site can provide a deeper understanding of the tomb and its historical significance.
Maebashi is also home to numerous other ancient burial mounds, including the Soja Kofun Group. Visiting several sites allows travelers to trace changes in regional leadership and burial customs over the course of the Kofun period.
A Window into the Beginnings of Ancient Kozuke
Maebashi Tenjinyama Kofun is an exceptionally important archaeological site representing the early development of keyhole-shaped burial mounds in eastern Japan.
The bronze mirrors associated with the Kinai region, together with the large quantity of iron weapons and tools, suggest that the ancient community of Kozuke was already connected to wider political and cultural networks during the first half of the 4th century.
Although only part of the original monument survives today, Maebashi Tenjinyama Kofun remains an indispensable site for understanding the ancient history of Gunma.
Standing quietly amid the modern city, the surviving remains offer a chance to imagine the powerful leaders, rituals, technologies, and long-distance connections that shaped this region more than 1,600 years ago.