Imashirozuka Kofun Tumulus

Imashirozuka Kofun is a Kofun period keyhole-shaped burial mound, located in the Gungeshinmachi neighborhood of the city of Takatsuki, Osaka in the Kinai region of Japan. The tumulus was designated a National Historic Site of Japan in 1958, with the area under protection expanded in 2006. It is the largest kofun in the Yodo River basin and one of the largest constructed in the first half of the sixth century. Although it has not been sanctioned by the Imperial Household Agency, there is a credible theory that it is the true tomb of the 26th Emperor Keitai.

Source: Wikipedia