Kofun

Kofun (古墳^?, from Sino-Japanese "ancient grave") are megalithic tombs or tumuli in Japan, constructed between the early 3rd century and the early 7th century AD. The term Kofun is the origin of the name of the Kofun period, which indicates the middle 3rd century to early-middle 6th century. Many Kofun have distinctive keyhole-shaped mounds (zenpō-kōen fun (前方後円墳^?)), which are unique to ancient Japan. The Mozu-Furuichi kofungun or tumulus clusters have been proposed for inscription on the UNESCO World Heritage List, while Ishibutai Kofun is one of a number in Asuka-Fujiwara similarly residing on the Tentative List.

The kofun tumuli have assumed various shapes throughout history. The most common type of kofun is known as a zenpō-kōen-fun (前方後円墳^?), which is shaped like a keyhole, having one square end and one circular end, when viewed from above. There are also circular-type (empun (円墳^?)), "two conjoined rectangles" typed (zenpō-kōhō-fun (前方後方墳^?)), and square-type (hōfun (方墳^?)) kofun. Orientation of kofun is not specified. For example, in the Saki Kofun group, all of the circular parts are facing north, but there is no such formation in the Yanagimoto kofun group. Haniwa, terracotta figures, were arrayed above and in the surroundings to delimit and protect the sacred areas.

...
Wikipedia