Nakaoyama Kofun

An octagonal tomb north of Takamatsuzuka

This tomb is in Hirata, Asuka Village, just north of Takamatsuzuka Kofun, famous for its murals.

It measures about 19 m between opposite sides. It is small even among Asuka's octagonal tombs, about half the size of the tomb of Emperor Tenmu and Empress Jitō (about 37 m).

The 2020 investigation

An excavation in 2020 confirmed that it is an octagonal tomb with a small stone chamber.

The mound was built in three tiers, and its outside was faced with stone. Small as it is, it was built with great care.

The tomb of Emperor Monmu?

The stone chamber was small, made to hold cremated bones. The tomb takes the highest-ranking shape, the octagon, yet holds a single cremated burial. On these two points, the leading theory is that it is the tomb of Emperor Monmu.

Emperor Monmu came to the throne in 697 and died in 707 at the age of 25. He was the emperor who issued the Taihō Code, Japan's early legal code. Among Japanese sovereigns who were cremated, he comes very early, second only to Empress Jitō.

The tomb the Imperial Household Agency designates as Emperor Monmu's, however, is Kurihara Tsukaana Kofun to the southwest. As with Kengoshizuka Kofun and the tomb of Empress Saimei, the official designation and the archaeological view do not agree.

Visiting

On 26 July 2026 it was inscribed as a World Heritage Site, as one of the components of "Asuka-Fujiwara: Archaeological Sites of Japan's Ancient Capitals and Related Properties."

About 15 minutes on foot from Kintetsu Asuka Station. It is a short way up the hill to the north of Takamatsuzuka Kofun.

The mound is covered for its protection, so you view its shape from outside.