175m keyhole mound in Kizugawa City (former Yamashiro Town). One of Japan's oldest definitive keyhole-shaped mounds (late 3rd–early 4th century), National Historic Site. Famous nationwide as a "trigger for the Yamatai Kingdom debate" due to 32+ triangular-rimmed divine beast mirrors among ~40 total bronze mirrors (Important Cultural Properties). The flagship ancient site of Kizugawa City.
Finds & research
~40 bronze mirrors incl. 32+ triangular-rimmed divine beast mirrors (Important Cultural Properties); weapons, armor, agricultural tools, fishing implements (~300 items total); split-bamboo-form wooden coffin. Distributed among Tokyo National Museum, Kyoto National Museum, and other institutions.
Two views on the occupant
Archaeological view
175m keyhole mound (rear circle ~110m, ~20m high) — a defining site of the earliest Kofun period. Pit-style stone chamber (~6.8m long, ~3m high) with a split-bamboo-form wooden coffin. ~40 bronze mirrors including 32+ triangular-rimmed divine beast mirrors — among the largest single-tomb assemblages in Japan. Famous in debates about the Yamatai Kingdom location; scholar Yukio Kobayashi's influential "same-mold mirror" theory was developed from this site. One of Japan's oldest definitive keyhole-shaped mounds.
Imperial Household Agency view
Not designated by the IHA. Designated as a National Historic Site in 2000. Artifacts (bronze mirrors) designated as Important Cultural Properties in 1992. Managed by Kizugawa City (former Yamashiro Town).
Field notes
The mound is forested with some access restrictions. About 10 min walk from JR Tanakura Station. Panel exhibits at Kizugawa City Library / History and Folklore Study Room. A must-visit for anyone interested in the Yamatai Kingdom debate.