National Historic Site: Hirui Otsuka Tumulus

The Hirui Otsuka Kofun is the largest keyhole-shaped burial mound in Gifu Prefecture, built approximately 1600 years ago. Its distinctive features include the mound's length of 150 meters, its three-tiered structure, and the presence of three different burial methods at the top of the circular rear section: a vertical shaft stone chamber, a clay burial chamber, and a direct burial in a wooden coffin. In the preservation and restoration work, the existing burial mound is being repaired, while a restoration zone has been created in a part of the rear circular section to restore the revetment stones, haniwa (clay figures), and surrounding moat. ◆ Date of construction of the burial mound: Late 4th century (Middle Kofun period) ◆ Scale of the burial mound: Mound length approximately 150 meters, rear circular section diameter 99 meters, height 13 meters, front rectangular section height 9.5 meters, total length including surrounding moat approximately 180 meters