Aozuka Tomb

Aozuka Kofun: A Majestic Keyhole-Shaped Tumulus from Ancient Owari

Rising gracefully from the western edge of the Inuyama alluvial fan in Aichi Prefecture, Aozuka Kofun is one of Japan's finest surviving examples of an early Kofun-period burial mound. Stretching 123 meters in length, this monumental keyhole-shaped tumulus is the second-largest ancient tomb in the prefecture and offers visitors a rare opportunity to walk through more than 1,600 years of layered history—from the powerful chieftains of the Owari region to the warlords of the Sengoku era.

Designated a National Historic Site in 1983, the mound today forms the centerpiece of the Aozuka Kofun Historic Park, where carefully reconstructed pottery cylinders, broad lawn promenades, and an on-site guidance facility bring the world of fourth-century Japan vividly to life.

A Window into the Mid-Fourth Century

Aozuka Kofun was built in the middle of the fourth century, during the early Kofun period—a formative era when emerging local rulers across the Japanese archipelago competed to demonstrate their authority through monumental tomb construction. The site was raised at the southwestern tip of a low terrace overlooking the Kiso River plain, a strategic and visually commanding location that would have made the tumulus a striking landmark for travelers and rivals alike.

Locally, the mound has long been associated with the deity Ōaratanomikoto, regarded by tradition as the divine descendant enshrined at nearby Ōagata Shrine, the second-ranking shrine of historic Owari Province. According to long-standing belief, the tumulus is the burial place of this revered ancestor, who is said to have opened up the lands of the Niwa region. Even today, a memorial rite known as the Bozensai is performed at the foot of the mound on a weekend close to the autumn harvest moon.

From Local Treasure to National Historic Site

The path to national recognition was not straightforward. In May 1966, Aozuka Kofun was first designated a cultural property by Inuyama City. Then, in 1979, the surrounding area was slated for agricultural land consolidation, raising urgent concerns about the tumulus's preservation. Local residents petitioned passionately for its protection, and a swift archaeological survey was carried out to confirm the mound's extent.

The investigation revealed extraordinary historical and academic value: the tomb's original form had survived remarkably well, and it offered crucial evidence of how political power was expressed in the Owari region during the fourth century. The site was duly excluded from the consolidation project, and on February 8, 1983, Aozuka Kofun was designated a National Historic Site by the Japanese government. Subsequent excavations between 1995 and 1998, followed by park development from 1996 to 2000, culminated in the opening of Aozuka Kofun Historic Park in August 2000.

Architectural Marvels of the Mound

Aozuka Kofun is a masterclass in early Kofun-period engineering. The mound was constructed entirely of layered earth, raised in steps over a broad rectangular base. The rear circular section is built in three tiers, while the front rectangular section rises in two. Investigators uncovered a distinctive construction method in which large river stones were stacked along the base of each tier, with smaller cobbles filling the space behind. The resulting facade has very few flat resting platforms—the tomb resembles, as one researcher put it, a layered mountain of stone, a building technique with few parallels elsewhere in Japan.

Visiting Aozuka Kofun Historic Park

The park is freely accessible and features an on-site guidance facility where visitors can examine excavated haniwa, replica bronze mirrors from the nearby Higashinomiya Kofun, and explanatory panels covering the broader archaeology of Inuyama. Curators are available during opening hours to provide commentary, although it is wise to call ahead for guided support. Hands-on workshops, such as crafting kofun-shaped erasers or keychains, are offered for a small fee.

Please note that climbing onto the mound itself is not permitted, in order to protect the historic fabric of the site. Visitors are welcome to walk the perimeter paths, picnic on the surrounding lawn, and observe the mound from carefully positioned vantage points.

Exploring the Surrounding Area

Inuyama is among the richest cultural landscapes in central Japan, and Aozuka Kofun pairs naturally with several outstanding attractions:

• Ōagata Shrine, the second-ranking shrine of old Owari Province, located about 3.5 kilometers east. Its main hall is a National Important Cultural Property and its grounds host more than 300 weeping plum trees that bloom from mid-February through mid-March.
• Inuyama Castle, a National Treasure originally built in 1537, whose timber keep is among the oldest surviving in Japan.
• Higashinomiya Kofun, a square-fronted tumulus considered one of the oldest of its kind in Aichi Prefecture, providing rich context for understanding regional Kofun-period developments.
• The Museum Meiji-mura, an open-air museum preserving more than sixty buildings from the Meiji era, including eleven National Important Cultural Properties.