Nishiyama Kofun, also known as Nagariyama or Magariyama, is an ancient burial mound located in Somanouchi-chō, Tenri City, Nara Prefecture. Built around the fourth century during the early Kofun period, it is one of the most distinctive archaeological sites in the region. The mound stands on the grounds of Tenri High School and was designated a National Historic Site of Japan in 1927.
With a total length of approximately 183 meters and an exceptionally unusual structure, Nishiyama Kofun offers valuable insight into the burial traditions, engineering skills, and political power of early Japanese elites. Its rare combination of architectural forms makes it particularly important to the study of ancient Japanese history.
Nishiyama Kofun belongs to the Somanouchi Kofun Group and is considered one of the earliest burial mounds constructed within the group. Dating to around the fourth century, it reflects the emergence of powerful political communities in the Tenri area during the early Kofun period.
The scale and elaborate design of the mound suggest that the individual buried there held a position of considerable authority. Although the person’s identity has not been established, the site provides important evidence of the political and cultural development of the ancient Yamato region, which became a major center of early Japanese state formation.
A vertical stone burial chamber, known as a tateana-shiki sekishitsu, was constructed near the center of the mound. However, the tomb had already been looted, and the original layout of the burial chamber is not fully understood.
During the Second World War, the former Japanese military reportedly used the mound as a position for anti-aircraft guns. Some of the stones from the burial chamber were excavated and removed during this period, further complicating efforts to reconstruct its original appearance.
Nishiyama Kofun measures approximately 183 meters in total length, making it one of the largest surviving examples of a zenpō-kōhō-fun, a burial mound with a rectangular front section and a rectangular rear section.
Its most remarkable feature is its three-tiered construction. The lowest tier has the form of a rectangular-fronted, rectangular-rear mound, while the middle and upper tiers take on the familiar keyhole shape, with a circular rear section and a rectangular front section. This unusual arrangement is extremely rare among Japanese burial mounds.
Lower tier: The rear section is square, measuring approximately 90 meters on each side, and is connected to a front section of the same length.
Middle tier: The circular rear section measures approximately 72 meters in diameter, while the front section extends for about 90 meters.
Upper tier: The summit forms a flat area approximately 30 meters in diameter. The front section continues at a level about 7 meters lower than the summit.
The complex arrangement is thought to reflect the mound’s original design rather than accidental changes over time. Its unusual architecture makes Nishiyama Kofun an important example of the diversity and experimentation seen in early Kofun-period tomb construction.
The mound was built on a gentle slope where three ridges meet. Rather than completely reshaping the terrain, its builders incorporated the natural contours into the design. The northern and southern ridges were used as parts of the outer embankment, demonstrating an effective use of the existing landscape.
A rectangular moat is believed to have surrounded the mound, although most of it has since been filled in. Some researchers have also suggested that the structure may be interpreted as a ryōtan-chūhō-fun, a burial mound with a central square section and rectangular projections at both ends. Its precise architectural classification remains a subject of academic discussion.
A variety of burial goods and other artifacts have been recovered from Nishiyama Kofun. Finds from the rear section include fragments of bronze mirrors, arrowheads made of green jasper, tubular beads, and fragments of iron swords and other blades.
A particularly unusual discovery was a sharinseki, a wheel-shaped stone ornament, found within the moat on the southern side of the front section. Objects of this kind are valuable evidence of the ornaments and ritual items associated with elite burials during the Kofun period.
The sloping surfaces of the mound were covered with fukiishi, stones used to protect and decorate the earthen structure. Excavations have also revealed a range of haniwa, the clay objects arranged around ancient burial mounds.
These include cylindrical haniwa, cylindrical examples with projecting fin-like decorations, and house-shaped haniwa. Together, these finds help researchers understand how burial mounds were decorated and how ritual practices expressed the status and authority of the deceased.
Nishiyama Kofun remains in relatively good condition. Because few trees grow on the mound itself, visitors can clearly observe the stepped construction and appreciate the distinctive outlines of its different tiers. Its monumental size and unusual combination of shapes make it a striking archaeological landmark.
For visitors interested in archaeology, ancient Japanese history, or the origins of Japan’s early political communities, the mound offers an opportunity to examine a rare form of burial architecture in its historical setting.
Nishiyama Kofun is approximately a 20-minute walk from Tenri Station, served by Kintetsu and JR railway lines. It lies about 500 meters south of the Tenri University Sankōkan Museum and immediately north of Tenri Junior High School, within the grounds of Tenri High School.
As the site is located on school grounds, visitors should respect school activities and any access restrictions in place.
Nishiyama Kofun was designated a National Historic Site on April 8, 1927. In 2018, the neighboring Nishinokurayama Kofun was added to the protected area, and the designation’s name was changed to the Somanouchi Kofun Group.
The expanded designation recognizes the broader archaeological significance of the area, where numerous ancient burial mounds preserve evidence of the powerful families and communities that flourished in the Tenri region.
Nishiyama Kofun is far more than an earthen mound. Its extraordinary three-tiered design, surviving structural features, and excavated burial goods reveal the sophistication of ancient builders and the importance of funerary traditions in early Japanese society.
Its unusual combination of rectangular and keyhole-shaped forms makes it a particularly valuable site for understanding the development of burial mound architecture during the fourth century. When exploring Tenri, a visit to Nishiyama Kofun offers a chance to reflect on the people, beliefs, and political power that shaped this part of Japan long before the emergence of the country in its later historical form.