A 100m keyhole mound just outside the outer moat on the north side of Daisen Kofun, 10.3m high at both the rear circle and the front section, laid out — like Daisen itself — along the western edge of the plateau with its front section to the south, and generally read as connected with Daisen. The IHA administers it as a satellite of the Nintoku mausoleum, though the fact that it is a large keyhole mound with a projection has led some to doubt that it is a satellite at all. The Agency for Cultural Affairs says the mound appears to have been built in three tiers, while Sakai City (its kofun database and the Sakai City Museum) gives two tiers. It is ringed by a moat, with a projection on the west of the waist and an earthen causeway across the moat on the east (whether the causeway is original is unclear). Constituent monument of the "Mozu-Furuichi Kofun Group" UNESCO World Heritage Site (2019). Managed separately from the main Daisen Kofun enclosure as a "detached" IHA site.
Finds & research
The mound is under Imperial Household Agency administration, and its burial facility and grave goods have not been revealed.
Official status & archaeological view
Official status
Managed by the IHA as a tobichi (detached parcel) satellite of the Nintoku Mausoleum. A baicho is a mound the IHA manages as attached to a principal tomb; several lie around Daisen Kofun. Tobichi indicates a parcel set apart from the main enclosure rather than directly adjoining it. The moat was designated a Sakai City Historic Site, the "Nagayama Kofun moat", in 2016.
Attribution (jitei): the Imperial Household Agency's determination of whose tomb it manages — separate from heritage designation.
Archaeological view
The Agency for Cultural Affairs dates it to the middle of the Middle Kofun period and the official World Heritage site to the first half of the 5th century; the Agency notes that no finds are known from it. The occupant has not been identified. Sakai City regards it as an independent medium-sized keyhole mound rather than a satellite tomb, since it has a projection and its front and rear sections are of equal size, and considers it likely to predate the adjacent Nintoku mausoleum mound.
Field notes
No entry, as the site is administered by the IHA; the mound can be viewed from the perimeter.