A Special Historic Site whose huge chamber is exposed after loss of the mound fill. The occupant is unknown, though an attribution to Soga no Umako is well known.
Finds & research
The chamber comprises more than thirty massive stones with a reported total weight of about 2,300 tonnes. It was looted, and the occupant and full grave assemblage remain unknown.
Two views on the occupant
Archaeological view
One of Japan’s largest square mounds, at Shimasho, Asuka. Investigations in 1933–35 identified the square mound, moat, and outer moat and showed that it was built around the beginning of the 7th century over smaller 6th-century tombs. Its exposed double-sleeved horizontal chamber is 19.1m long; the largest ceiling stone weighs about 77 tonnes.
Imperial Household Agency view
This is not an IHA mausoleum. It is a National Special Historic Site whose chamber can be entered during paid opening hours. It became a component of the World Heritage property Ancient Capitals of Asuka and Fujiwara in 2026.
Field notes
Current guidance gives hours of 9:00–17:00, with last admission at 16:45, year-round. Check Asuka Historical National Government Park for current fees and changes.