A National Historic Site known for its finely dressed horizontal chamber. The mound is about 40m per side according to the 1978 Kashihara Archaeological Research Institute excavation (other estimates suggest about 45m).
Finds & research
A double-sleeved horizontal chamber of dressed stone survives. Proposed occupants include Princess Kibitsuhime, Kose no Okara no Sukune, and Empress Saimei, but none is established.
Two views on the occupant
Archaeological view
A square mound at Koshi, Asuka. Excavations by the Kashihara Archaeological Research Institute in 1978 confirmed it at about 40m per side, about 12m high, and two-tiered (other sources suggest about 45m). Its nearly south-facing horizontal chamber is built from finely dressed and polished stones. Asuka Village dates it to the early 7th century and calls this chamber form the Iwayayama type.
Imperial Household Agency view
This is not an IHA mausoleum. It was designated a National Historic Site on 11 May 1968. Several occupants have been proposed, but none is established.
Field notes
Chamber access may change; check current Asuka Village guidance and on-site signs before entering.