Hakkaku-fun Tumulus (八角墳)
Hakkaku-fun is a regular octagonal tumulus constructed during the end of the Kofun period (around the mid seventh century). Well known tumuli of this type are Gobyono-kofun Tumulus (present-day Tumulus of the Emperor Tenji) in Kyoto City, and Noguchino Ono-haka-kofun Tumulus (present-day Joint Tumulus of the Emperor Tenmu and the Empress Jito) in Asuka-mura, Takaichi-gun, Nara Prefecture.
Meaning of Octagonal Tumuli
The octagonal tumuli are considered to have been made based on the idea that the octagon suits a king who shows his ruling power in eight (all) directions of the world, which came from Chinese political philosophy in general.
The octagonal tumuli are included in the dead end types of tumulus in its history according to Koichi MORI. Although some archaeologists indicate that they were possibly dedicated to enthroned kings, many doubt that they were only for enthroning kings, because similar tumuli, if in a small number, were discovered not only in Nara Prefecture, but also in the eastern part of Japan, such as at Inarizuka-kofun Tumulus in Tama City, Tokyo Prefecture.
The Emperor Jomei's tomb is thought to have been the first octagonal tumulus, so one can assume that a unique type of tumulus for the kings of Yamato was invented. It was to declare the king as the top ruler different from other local powerful lords of clans, with the aim of establishing a nation of centralized governance structure.
On April 19, 2006, news media reported that a group of twenty-four buried tombs of the seventh century was detected in the Kuwanohara-kofun Tumuli of Kuwanohara-iseki Ruins in Ibaraki City, Osaka Prefecture, and an archaeologist remarked one of them was octagonal and might be NAKATOMI no Kamatari's tomb.
Tumuli of Kings
Dannozuka-kofun Tumulus (present-day Tumulus of the Emperor Jomei): Sakurai City, Nara Prefecture
Gobyono-kofun Tumulus (present-day Tumulus of the Emperor Tenji): Kyoto City
Noguchino Ono-haka-kofun Tumulus (present-day Joint Tumulus of the Emperor Tenmu and the Empress Jito): Asuka-mura, Takaichi-gun, Nara Prefecture; the last half of the seventy century; an octagonal tomb on a rectangular basement
Nakaoyama-kofun Tumulus (likely to be Tumulus of the Emperor Monmu): Asuka-mura, Nara Prefecture; the beginning of the eight century
Tsukamyojin-kofun Tumulus (likely to be Mayumiyama-ryo Tumulus of Prince Kusakabe, and possibly, octagonal): Takatori-cho, Takaichi-gun, Nara Prefecture
Iwayayama-kofun Tumulus (likely to be Tumulus of Empress Saimei; likely to be an octagonal tomb on a rectangular base)
Tumuli of Chieftains
Inarizuka-kofun Tumulus: Mogusa, Tama City, Tokyo Prefecture; the first half of the seventh century
Mitsuya-kofun Tumulus: Yoshioka-machi, Kitagunma-gun, Gunma Prefecture; the first half of the seventh century
Kyozuka-kofun Tumulus: Fuefuki City (former Ichinomiya-cho), Yamanashi Prefecture; discovered in 1994; the first half of the seventh century
Isezuka-kofun Tumulus: Fujioka City, Gunma Prefecture; the first half of the sixth century
Nakayamasoen-kofun Tumulus: Takarazuka City, Hyogo Prefecture
Tumuli that are Indicated to be Octagonal
Oichi Ichigo-kofun Tumulus (First Tumulus of Oichi): Shinichi-cho, Fukuyama City, Hiroshima Prefecture
Jinbo Ipponsugi-kofun Tumulus: Yoshii-machi, Tano-gun, Gunma Prefecture