Kofun are megalithic tombs or tumuli in Northeast Asia. Kofun were mainly constructed in the Japanese archipelago between the middle of the 3rd century to the early 7th century CE.
The term 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 (前方後円墳). The Mozu-Furuichi kofungun or tumulus clusters were inscribed on the UNESCO World Heritage List in 2019, while Ishibutai Kofun is one of a number in Asuka-Fujiwara 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, which is shaped like a keyhole, having one square end and one circular end, when viewed from above. There are also circular-type (empun), "two conjoined rectangles" typed (zenpō-kōhō-fun), and square-type (hōfun) 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.
Kofun range from several metres to over 400 m long. The largest, which has been attributed to Emperor Nintoku, is Daisen Kofun in Sakai City, Osaka Prefecture.
The funeral chamber was located beneath the round part and comprised a group of megaliths. In 1972, the unlooted Takamatsuzuka Tomb was found in Asuka, and some details of the discovery were revealed. Inside the tightly assembled rocks, white lime plasters were pasted, and colored pictures depict the 'Asuka Beauties' of the court as well as constellations. A stone coffin was placed in the chamber, and accessories, swords, and bronze mirrors were laid both inside and outside the coffin. The wall paintings have been designated national treasures and the grave goods as important cultural property, while the tumulus is a special historic site.