Miyakozuka Kofun is an ancient burial mound located in Sakata, Asuka Village, Takaichi District, Nara Prefecture. Also known as Kintorizuka, this square-shaped tomb is believed to date from the latter half of the 6th century, during the Late Kofun period. Designated a National Historic Site, it is an important archaeological landmark that offers clues to the political power, burial customs, and international connections of ancient Japan.
The village of Asuka is renowned for its archaeological remains, ancient shrines, and Buddhist temples, many of which illuminate the formative years of Japanese civilization. Miyakozuka Kofun adds to this rich heritage, particularly through its unusual stepped stone construction and its possible connection to the influential Soga clan.
Miyakozuka Kofun was built during a period of transition in Japanese burial traditions. Large keyhole-shaped burial mounds had dominated earlier centuries, but by the 6th century, square mounds and other forms were becoming increasingly prominent. The design of Miyakozuka Kofun reflects these changing practices and the emergence of new architectural influences.
The construction project is sometimes estimated to have required the labor of approximately 30,000 people. Although such a figure is an estimate, the scale of the undertaking suggests that the person commemorated by the tomb belonged to a powerful social group capable of mobilizing substantial resources and manpower.
The reconstructed dimensions of Miyakozuka Kofun are approximately 41 meters from east to west and 42 meters from north to south, with a height of at least 4.5 meters. Its most distinctive feature is the stepped arrangement of stones covering the mound’s exterior, giving it an unusual terraced appearance.
Researchers have pointed to similarities between this construction and stepped stone burial mounds found in Goguryeo and Baekje on the Korean Peninsula during the 5th century. These parallels have attracted interest because they may reflect the movement of architectural ideas and cultural practices across East Asia during ancient times.
A surrounding moat encircles the mound. It measures approximately 1–1.5 meters wide and reaches around 0.4 meters in depth. Although its precise function is not fully established, the moat formed part of the tomb’s overall layout and helped define the boundary around the burial mound.
The burial facility is a horizontal stone chamber with entrances on both sides of its front section, known in Japanese archaeology as a ryōsode-shiki yokoguchi-shiki sekishitsu. It opens toward the southwest and measures approximately 12.2 meters in total length. The main burial chamber is about 5.3 meters long, 2.8 meters wide, and 3.55 meters high.
At the center of the chamber stands a hollowed, house-shaped stone coffin carved from tuff quarried from Mount Nijo. The coffin body measures approximately 2.23 meters long, 1.46 meters wide, and 1.08 meters high, with a total height of around 1.72 meters. A stone support for the coffin was also present. The possibility that a wooden coffin was used for a later burial has been suggested, although this remains uncertain.
The burial chamber was disturbed by grave robbers, and most of its original grave goods have been lost or scattered. Nevertheless, archaeological investigations have recovered iron objects and other materials that provide clues to the tomb’s use and the burial practices of its period.
Finds associated with the site include Haji pottery, Sue pottery, iron implements such as small knives, iron arrowheads, iron nails, and small armor plates, as well as glazed ceramic vessels. These objects help researchers investigate the technologies, material culture, and social customs of people living in the region during the late 6th century.
The entrance to Miyakozuka Kofun’s stone chamber faces in the same general direction as the chamber entrance at nearby Ishibutai Kofun. This similarity, together with their proximity, has prompted discussion about possible relationships between the two burial sites.
One intriguing theory identifies the occupant of Miyakozuka Kofun as Soga no Iname, a powerful political leader of the 6th century. Iname was a prominent member of the Soga clan, which played a major role in the introduction and development of Buddhism and in the politics of the early Japanese court.
The tomb’s estimated construction date and location have contributed to this hypothesis. However, there is no conclusive evidence confirming that Soga no Iname was buried here, and the identity of the occupant remains unknown. The theory nevertheless makes Miyakozuka Kofun an especially interesting site for understanding the influence of the Soga family during a pivotal period in Japanese history.
Miyakozuka Kofun is located relatively close to Ishibutai Kofun, one of Asuka’s best-known ancient tombs. Ishibutai is widely associated with Soga no Umako, the son of Soga no Iname. Because the two tombs are near each other and share certain structural characteristics, some researchers have suggested that they may be connected as the burial places of members of the same family.
Under this interpretation, Miyakozuka Kofun could have been the tomb of Soga no Iname, while Ishibutai Kofun may have served as the burial place of his son, Umako. This remains a hypothesis rather than a confirmed identification, but it offers a fascinating perspective on the possible concentration of elite Soga family burials in the Asuka area.
Miyakozuka Kofun was designated a National Historic Site of Japan in 2017, formally recognizing its archaeological and historical importance. Preservation and research efforts help protect the remains and support further investigation into its construction, burial chamber, and possible historical associations.
Miyakozuka Kofun is a valuable destination for travelers interested in archaeology and the early history of Japan. Its square form, stepped stone exterior, and substantial burial chamber reveal a sophisticated approach to tomb construction during a period of significant political and cultural change.
Its possible connection to Soga no Iname and the nearby Ishibutai Kofun adds another layer of historical intrigue. While many questions remain unanswered, visiting Miyakozuka Kofun offers an opportunity to explore the mysteries of the Kofun period and appreciate Asuka’s enduring importance as one of the key centers of ancient Japanese civilization.