[1] The Iwayayama Kofun has been widely known since ancient times because of the opening of the horizontal-entry stone burial chamber, which was robbed in antiquity.

It was long thought to be a square hōfun (方墳)-style tumulus with 45-meter sides, but modern archaeological techniques indicate that it was mostly likely originally square in the lower section, but with an octagonal upper section.

[2] It has been estimated that the construction period of Iwayayama Kofun was from around the middle of the 7th century to the third quarter of the 7th century, based on the type of house-shaped sarcophagi, and the chronology of Sue ware pottery excavated from similar tombs, and it has been suggested that this may have been the tomb of Empress Saimei, based on its unusual style, which was typically only used for royal tombs during this period.

On the other hand, based on the assumption that the Eifuku-ji Kita Kofun is indeed the tomb of Prince Shotoku, who died in 621 or 622 AD, this would move the construction of this tumulus to the first quarter of the 7th century, which would rule out the possibility that it was the tomb of Empress Saimei.

The tumulus is about two minutes on foot from Asuka Station on the Kintetsu Railway Yoshino Line.