An exceptionally distinctive keyhole mound whose front section reaches nearly twice the width of the rear circle—a "wide front-section type." Total length 115m with three-tiered construction, stone covering, and haniwa rows. A visually striking illustration of the rapid development of front sections in the late Kofun period. It stands adjacent to Takayatsukiyama Kofun, forming a pair of major mausolea at the southern end of the Furuichi group. Emperor Seinei is known for the succession crisis that preceded Emperor Keitai's accession: Seinei left no heir, and Princess Iiyotoao briefly administered affairs before Emperors Kenzo and Ninken restored the line—one of the most dramatic episodes in the chronicles. Although not included in the 49 World Heritage constituent monuments, this mound is indispensable for understanding the Furuichi group.
Finds & research
No excavation permitted under IHA mausoleum regulations. Internal structure and grave goods remain unknown. Exterior viewable from public paths.
Two views on the occupant
Archaeological view
The actual occupant is unknown. The unusually wide front section—roughly twice the diameter of the rear circle—is a hallmark of the late-Kofun period and a classic example of the trend toward expanding front sections in the 5th–6th centuries. Cylindrical and figural haniwa have been confirmed. Total length 115m, rear circle ~63m. Some researchers note a slight discrepancy between Emperor Seinei's traditional reign dates (c. 480s) and the mound's estimated construction date (early 6th century), calling the IHA attribution into question.
Imperial Household Agency view
Managed by the IHA as the mausoleum of Emperor Seinei (22nd Emperor). Formally named Kawachi-Sakato-no-Hara-no-Misasagi. Emperor Seinei died without issue, marking a critical moment of succession crisis in the early imperial lineage. The IHA manages access, prohibiting general entry.[IHA Visiting Info] Address: 大阪府羽曳野市西浦6丁目 / Access: 近鉄 古市駅から徒歩約18分 / Hours: 原則、8時30分～17時 (open year-round in principle). Stamp storage: 古市陵墓監区事務所.
Field notes
Together with the adjacent Takayatsukiyama Kofun, it preserves the southern end of the Furuichi landscape.