| Location | Sakai, Osaka |
|---|---|
| Shape | Keyhole-shaped mound |
| Mound length | 486 m |
| Period | Early–mid 5th c. |
| Designation | Imperial Tomb (IHA) |
| World Heritage | Mozu-Furuichi Kofun Group (UNESCO) |
| IHA designation | IHA-managed (no public entry) |
At 486m in the published Sakai City and Agency for Cultural Affairs figures, this is Japan's longest burial mound. An IHA survey measured 525.01m at the present floor of the first moat, but does not treat that figure as the original mound length. The three-tiered keyhole mound rises to about 35.8m at the rear circle (about 249m across) and 33.9m at the front section (about 307m wide) in Sakai City's figures. It is the only giant keyhole mound ringed by triple moats, and the total area including water reaches about 47 hectares — roughly 12 Koshien Stadiums. Stone-paved slopes (fukiishi) once covered the mound, and rows of cylindrical haniwa were set on the summits, at the waist and at the end of the front section. Its footprint exceeds even that of the Great Pyramid of Giza, though its volume (about 1.4 million m³) is smaller than the pyramid's (about 2.6 million m³). Inscribed in July 2019 as part of the "Mozu-Furuichi Kofun Group" UNESCO World Heritage Site (Japan's 23rd WHS). Note: "Nintoku Tenno-ryo" is the name based on the IHA's attribution; archaeologists distinguish it as "Daisenryo Kofun" or "Daisen Kofun." Some rank this alongside the Great Pyramid and the First Emperor's Mausoleum as one of the world's three greatest tombs.
The rear-circle burial is uninvestigated; the pit-style stone chamber and nagamochi-gata sarcophagus exposed on the south slope of the front section in 1872 were recorded along with gilt copper-plate armour, glass vessels and other items, and then reburied. Cylindrical and figural haniwa (human figures, horses, roosters, boats), Sue ware, Haji ware, and beads have been recovered from the outer embankment and outer moat. The haniwa from the outer embankment are particularly well preserved and are exhibited at the Sakai City Museum. Joint IHA/Sakai City excavations from 2018 onward have documented the outer embankment but no investigation of the mound interior has been carried out.
A moat-side promenade circles the outer moat in about 2.8km (40 min walk). The Sakai City Museum in adjacent Daisen Park displays haniwa and related finds. A free observation deck on the 21st floor of Sakai City Hall offers a bird's-eye view of the entire mound.