A Special Historic Site whose huge chamber is exposed after loss of the mound fill. The occupant is unknown, though the Asuka Historical National Government Park and Nara Prefecture both introduce the view that it is the tomb of Soga no Umako.
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.
Official status & archaeological view
Official status
It is a National Special Historic Site. It became a component of the World Heritage property Ancient Capitals of Asuka and Fujiwara in 2026.
Archaeological view
One of Japan’s largest square mounds, at Shimanosho, Asuka; Asuka Village gives its side as about 50m and Nara Prefecture as about 55m (ringed by a dry moat 5.9–8.4m wide). Investigations in 1933–35 identified the square mound, moat, and outer moat; the mound is thought to have been built around the beginning of the 7th century, destroying smaller 6th-century tombs. Its exposed double-sleeved horizontal stone chamber is 19.1m long; the largest ceiling stone weighs about 77 tonnes. Nara Prefecture’s heritage database notes that, given its scale, date and location at Shimanosho, it is thought likely to be Soga no Umako’s Momohara tomb.
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. The chamber can be entered for a fee during opening hours.