A giant keyhole mound spanning Matsubara and Habikino. It is 335m long; the front section is 230m wide and 4m high, and the rear circle is 185m across and 20m high. A moat surrounds it. Regarded as the last giant keyhole mound built in the Furuichi group, it is administered by the Imperial Household Agency as the Otsuka imperial mausoleum reference site.
Finds & research
A large boulder known as Gobo-ishi, thought to be a ceiling stone from a horizontal stone chamber, remains on the rear circle. Documents also indicate that part of a horizontal chamber was open until the late 18th century, but the complete burial facility and grave goods are unknown.
Two views on the occupant
Archaeological view
The unclear evidence for haniwa, the low and widely flaring front section, and indistinct tiers on the rear circle are late-period traits, leading to a date in the mid-6th century or later. The occupant is unidentified.
Imperial Household Agency view
The site became the Otsuka imperial mausoleum reference site on September 21, 1925, and is administered by the Imperial Household Agency. An official government reply lists the occupant as unknown; it is not designated as the tomb of any particular emperor. The mound spans Matsubara and Habikino, is not freely accessible, and has not undergone an academic excavation.