A beautiful octagonal mound characteristic of the imperial tombs of this era. Until recent years, the mound had collapsed and the stone chamber was exposed, but archaeological research has accurately reconstructed its appearance at the time of construction, and it was opened to the public in 2022.
This tumulus is the tomb of Empress Saimei, the leading character of this tour. There are two stone chambers and based on the description in Japan's oldest history book, Chronicles of Japan, it is thought that her daughter was buried here as well. Her granddaughter was buried in the nearby Koshizukagomon Tumulus.

Tuff, softer than granite, is used for the stone chambers of the former tumulus. The design, material and construction techniques can be said to be the culmination of Asuka's gigantic stone culture.

The unearthed cloisonné metal fittings are the oldest extant items in East Asia, and can be seen at the Exhibition Room of Archaeological Cultural Properties and the Asuka Historical Museum in the village.