| Location | Osaka Pref. |
|---|---|
| Shape | Keyhole-shaped mound |
| Mound length | 210 m |
| Period | Early 5th c. |
The southernmost keyhole mound in Osaka Prefecture (210m). Three-tiered construction on a hilltop in Misaki-cho, Sennan-gun, with panoramic views of Osaka Bay and Awaji Island. Dated to the early 5th century with a surrounding moat. Not excavated due to IHA management as a reference site. Together with the nearby Tannoha Nisanzai Kofun (173m), it forms the core of the "Tannoha kofun group," believed to have been the base of an ancient maritime power. In ancient times this was the strategic southern gateway of Osaka Bay, a hub of the maritime network linking Kii, Shikoku, and Awaji.
IHA-designated reference site (Tannoha Ryobo Sankochi); excavation prohibited. From exterior observation, the mound uses the natural hillside (~50m elevation) and shows a three-tiered form; traces of the surrounding moat are visible. Its commanding position overlooking Osaka Bay and Awaji Island is taken as evidence that the occupant controlled 5th-century maritime routes. Internal burial structure and grave goods unknown. Together with the nearby Udohaka Kofun (Tannoha Nisanzai, 173m), this forms the Tannoha kofun group at the southern tip of Osaka Prefecture.
Misaki-cho remains the southernmost point of Osaka Prefecture, known as the departure point for ferry routes to Awaji Island. The mound's overall form can be appreciated by walking the exterior perimeter, but entry is restricted.