The Atagoyama Yokoana Tomb Group is a collection of ancient tunnel tombs located in Taihaku Ward, Sendai City, Miyagi Prefecture. The tombs are believed to date from the late 7th century to the early 8th century, during the latter part of Japan’s Kofun period and the transition toward the Nara period.
These tombs were carved into the slopes of Mount Atagoyama. Some openings can still be seen today, while others remained buried underground until they were discovered through archaeological investigations. Unfortunately, some tombs were also destroyed during later construction and urban development.
The total number of tombs is still uncertain. Among them are particularly valuable decorated tunnel tombs whose burial chambers were painted with red pigment. These remains provide important clues about the burial customs, beliefs, and social structure of people who lived in the Sendai area more than 1,300 years ago.
Mount Atagoyama rises along the western edge of the Sendai Plain, where a series of hills extends into the lowland near the Hirose River. The tunnel tombs are concentrated mainly on the northern slope and on the eastern part of the southern slope. Collectively, these archaeological remains are known as the Atagoyama Yokoana Tomb Group.
Across the Hirose River to the south lies another group of tunnel tombs known as the Oterayama Yokoana Tomb Group. Other groups, including the Futatsuzawa Yokoana Tomb Group and Mogasaki Yokoana Tomb Group, are also located around Oterayama, while the Sozenji Yokoana Tomb Group lies along the Hirose River.
These archaeological sites are collectively referred to as the Mukaiyama Yokoana Tomb Groups. The area was part of the cultural center of ancient Mutsu Province, and the Atagoyama tombs are thought to have belonged to this broader cultural sphere.
The Atagoyama tunnel tombs are generally estimated to have been constructed from around the late 7th century to the early 8th century.
At that time, the regional government center of Mutsu Province was located at the Koriyama Site, approximately 2 kilometers southeast of Mount Atagoyama. The tunnel tombs are therefore thought to have been built for local influential people and their families who lived in or around the settlements associated with this administrative center.
The close relationship between the tombs and the ancient government center offers an important glimpse into the social hierarchy and political landscape of northeastern Japan during this period.
The tombs were carved directly into the middle sections of mountain slopes. From the entrance, a passage known as a sendō leads inward. This passage is approximately 1 meter wide in many examples.
The passage may lead through a narrower entrance area known as a genmon before reaching the main burial chamber, or genshitsu. Some tombs do not have a distinct genmon, but the basic arrangement is generally similar.
The burial chambers are generally square or trapezoidal in shape, sometimes with rounded corners. Their dimensions are usually within a range of approximately 1 to 3 meters per side.
One example was found with part of its floor covered with stones. Although many of the chambers have not survived in good condition, archaeological investigations have uncovered burial goods including iron swords, iron arrowheads, Sue ware pottery, Haji ware pottery, and glass beads.
These objects provide valuable information about the people buried in the tombs and the material culture of the period.
One of the most remarkable remains in the Atagoyama Yokoana Tomb Group is a decorated tunnel tomb discovered near the southeastern slope.
The tomb has a passage approximately 2.5 meters long. The burial chamber is almost square, measuring approximately 1.9 meters deep by 1.8 meters wide, with an estimated height of about 1.4 meters.
The ceiling is thought to have been either house-shaped or dome-shaped. The entrance to the burial chamber had been sealed with stones.
The rear wall of the burial chamber was decorated with red pigment. Numerous patterns consisting of circles and circle-and-cross motifs were painted across the wall.
The motifs were not arranged according to a strict geometric pattern but were distributed relatively freely across the surface. Their exact meaning remains uncertain, but they are thought to have had some connection with the status, beliefs, or funerary practices of the person buried there.
Archaeologists recovered a Haji ware cup, a small iron knife, human remains representing five individuals, fragments of Sue ware and Haji ware, and other iron objects.
The tomb is estimated to date from around the middle to late 7th century. Its construction and contents suggest that it may have been the burial place of a person or family of considerable status in the local community.
The tunnel tombs of Mount Atagoyama had been known to local residents for many years. A map published in 1912 identified some of the tombs on the northern side as “Ezo-ana,” or “Ezo caves.”
In 1936, numerous tunnel tombs were discovered during road construction. Human bones, straight swords, and Sue ware pottery were recovered, although many of these artifacts were subsequently dispersed and their original archaeological context was lost.
In 1937, archaeologist Toshishiro Shimizu conducted an investigation of the site. A total of 34 tunnel tombs were identified across the southeastern and northern slopes.
By that time, however, some of the tombs had already been damaged or destroyed, making it difficult to determine their exact original locations and total number.
During World War II, some of the open tombs were reused as air-raid shelters. After the war, some were used as storage spaces.
As Sendai expanded and residential development progressed, however, many of the remaining tombs were destroyed. These changes made subsequent archaeological investigations increasingly important for documenting what remained.
In 1973, road construction associated with the building of Atago Bridge led to an archaeological survey of the southern slope. Ten tunnel tombs were identified, and nine of them were excavated.
Artifacts including Sue ware pottery and human remains were recovered during the investigation.
In April 1976, an opening unexpectedly appeared during road construction, revealing human remains inside. An emergency excavation was carried out, and the tomb was identified as the important decorated tunnel tomb.
Although its archaeological and cultural value was recognized, preservation arrangements were not yet sufficiently established at the time. After the investigation was completed, the tomb was therefore reburied.
In 1991, another archaeological survey was conducted before residential construction. Eighteen tunnel tombs were discovered, and fifteen were investigated.
Artifacts including straight swords and glass beads were recovered. Many of the tombs, however, had already suffered partial damage or destruction.
Many of the surviving tunnel tombs are now hidden beneath forested slopes or within areas affected by residential development. Some openings remain visible, allowing visitors to observe their entrances from outside.
However, the site is not a conventional archaeological park with all tombs open to the public. Some locations are on private property or in potentially dangerous areas, and access may therefore be restricted.
The tombs were carved into natural hillsides, so visitors should be aware of potential hazards such as unstable ground, steep slopes, and falling or collapsing earth and rock.
For this reason, visitors should follow guidance from the local authorities or educational and cultural heritage organizations and obtain permission where necessary. Rather than entering or approaching restricted areas on their own, it is important to respect the archaeological site and its surrounding environment.
The Atagoyama Yokoana Tomb Group is an important archaeological heritage site that provides clues about the lives, beliefs, and burial customs of people in ancient northeastern Japan.
The decorated tomb, with its mysterious red-pigment motifs, is particularly valuable for understanding the funerary culture of the period. The artifacts recovered from the tombs also reveal connections between local communities and the wider cultural world of ancient Mutsu Province.
Although many of the tombs are now hidden underground or have been lost to development, the surviving remains preserve a story that reaches back more than 1,300 years. For visitors interested in archaeology and the ancient history of the Tohoku region, the Atagoyama Yokoana Tomb Group offers a fascinating glimpse into a little-known chapter of Japan’s past.