Jinbayama Kofun
Japan
Jinbayama Kofun is a Kofun period keyhole-shaped burial mound, located in the Nobuyuki neighborhood of the city of Shimonoseki, Yamaguchi in the San'yō region of Japan. The tumulus was designated a National Historic Site of Japan in 1991. It is the largest burial mound in the Nagato region (western Yamaguchi Prefecture) and the third largest in Yamaguchi Prefecture, and is estimated to have been built in the latter half of the 4th century (the first half of the Kofun period).
Monument data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).