Gobyono-kofun Tumulus (御廟野古墳)
There is no doubt that this is the tumulus of an Emperor who was a real person in history, in other words, this tomb can be called 'the Imperial mausoleum of Emperor Tenchi.'
This kind of identified tomb is extremely rare; the only other example is Noguchi no O no Haka Tumulus, the joint tumulus of the Emperor Tenmu and the Empress Jito.
Only tombs of major kings were octagonal during the middle of the seventh century. Tombs of horizontally octagonal mounds that have been found are: Dannozuka-kofun Tumulus (present-day Jomei-ryo Tumulus) in Sakurai City of Nara Prefecture; Noguchi no O no Haka Tumulus (Joint Tumulus of the Emperor Tenmu and the Empress Jito) in Asuka-mura, Takaichi-gun, Nara Prefecture; Nakaoyama-kofun Tumulus which is commonly thought to be Monbu-ryo Tumulus in Asuka-mura, Nara Prefecture; and the Gobyono-kofun Tumulus. This fact shows that a unique type of tumulus for Kings in Japan, was invented for the first time in history.
Other tombs that follow, may be octagonal: Tsukamyojin-kofun Tumulus (likely to be Mayumiyama-ryo Tumulus of Prince Kusakabe) in Takatori-cho, Takaichi-gun, Nara prefecture; and Iwayayama-kofun Tumulus (likely to be Saimei-ryo Tumulus) which probably consist of an octagonal mound.