A White Octagonal Mound on the Hills of Asuka
Walk west from Asuka Station for about ten minutes and the ground rises toward a low ridge once called Mayumi Hill. Near its top sits a structure unlike almost any other ancient tomb in Japan: a mound with eight straight sides, faced entirely in pale, near-white stone, its tiered base ringed by neatly cut blocks. This is Kengoshizuka Kofun, and the form visitors see today was reconstructed and opened to the public in March 2022, after a restoration program that ran for five years.
The shape carries the meaning. In seventh-century Japan, octagonal mounds were reserved for sovereigns and those closest to them. Kengoshizuka is widely thought to be the resting place of Empress Saimei, the first sovereign in Japanese history to take the throne twice, buried alongside her daughter. A few steps to the southeast lies a second, smaller tomb, Koshizuka Gomon Kofun, identified only in 2010. The two were designated together as a National Historic Site, and together they match a story recorded in Japan's oldest official chronicle.
An Eight-Sided Tomb Rebuilt from the Evidence
Kofun are the earthen burial mounds raised across Japan between roughly the third and seventh centuries. Most are round or keyhole-shaped. The octagonal mound appeared late, during what archaeologists call the Terminal Kofun period, and it is tied closely to the imperial line. Excavations by the Asuka Village Board of Education between 2009 and 2011 confirmed that Kengoshizuka was octagonal, measuring about 22 meters between opposite faces and standing at least 4.5 meters high.
The builders raised the mound in compacted earthen layers, a technique called hanchiku. Around its base they set cut blocks of tuff quarried from Mount Nijo, and on the western side archaeologists found a double apron of river stones. The brilliant white surface visible now is a modern restoration, but it follows the excavated evidence closely, which is why the rebuilt mound drew attention well beyond the usual circle of archaeology enthusiasts.
An old nickname captures the effect. Seen from above, the eight-petalled form resembled a morning glory, and the tomb was long known locally as Asagaozuka, the Morning Glory Mound. The word kengoshi is itself an archaic name for the morning glory seed.
Two Chambers Carved from a Single Stone
What sealed Kengoshizuka's importance lies inside the mound. The burial chamber is a yokoguchi-shiki sekkaku, a stone sarcophagus entered from the side, and it was hollowed out of one enormous block of rhyolitic tuff breccia. Rather than a single space, the interior was cut into two rooms divided by a central wall. Each room held a coffin platform sized for an adult, the eastern at about 195.5 by 81.5 centimeters and the western at about 195.0 by 80.0 centimeters, almost identical. A tomb built from the outset for two people is itself unusual.
The entrance was closed twice over, with an inner blocking stone and a larger outer one of quartz andesite measuring roughly 245 by 270 centimeters, and the whole chamber was framed by rectangular cut stones. The tomb was robbed in antiquity, yet excavators still recovered fragments of a dry-lacquer coffin, known as a kyocho coffin and made by layering lacquered cloth, along with cloisonné metal fittings in a tortoiseshell pattern, gilt-bronze flower-shaped mounts, and many glass beads. Among the human remains were teeth whose measurements fall close to the female average, from a person aged roughly 30 to 40.
An Empress, Her Daughter, and the Chronicle's Account
The leading theory names the two occupants as Empress Saimei and her daughter, Princess Hashihito. Saimei first reigned as Empress Kogyoku, abdicated, then later returned to the throne under the name Saimei. She died in 661 in Kyushu while preparing to send forces in aid of the kingdom of Baekje on the Korean peninsula, and her body was carried back to Asuka.
The Nihon Shoki, compiled in 720, records under the sixth year of Emperor Tenji that Saimei and Princess Hashihito were buried together at a tomb called Ochi-no-oka-no-e, and that Princess Ota was laid to rest in front of it. That single sentence fits the ground remarkably well. The smaller tomb southeast of Kengoshizuka, Koshizuka Gomon Kofun, is thought to be the grave of Princess Ota, a granddaughter of Saimei and a consort of the future Emperor Tenmu. Because its grave pit was cut into earth already piled for Kengoshizuka, the larger tomb must have come first, in keeping with the chronicle's order of events.
Koshizuka Gomon is a small square mound, roughly ten meters on a side, with its own side-entry stone chamber hollowed from a massive block of quartz diorite, a local stone sometimes called Asuka stone. Its chamber runs about 2.4 meters deep, and a sloping passage with a covered drainage channel led up to the entrance. Lacquer film and iron objects were among the finds.
Visiting the Site
The grounds are free, and the path runs through the site at any hour. Both stone chambers can be viewed from outside their gates, and a short film about Koshizuka Gomon plays on site during the day. For a closer look, the Asuka Tourist Association runs guided viewings of the chambers by advance reservation. There is no parking at the tomb itself, so drivers usually leave their cars at the Asuka roadside station or the nearby Agri Station and walk the short distance up the hill.
The walk from Asuka Station passes other monuments worth a stop. Iwayayama Kofun, whose finely cut stone chamber you can step inside, lies along the way, and the wider Asuka basin is dense with palace sites, temples, and carved stones from the same era. Renting a bicycle near the station is a common way to link them.
- 📍 Plan Your Visit to Nara
- Find tours, activities & transport passes near Kengyokozuka Tomb and Koshizukamikado Tomb
- [ Todaiji Great Buddha & Nara Park Deer Experience ]
Q&A
- Who is buried at Kengoshizuka Kofun?
- The strongest theory holds that it is the joint tomb of Empress Saimei and her daughter Princess Hashihito. The identification rests on the octagonal form reserved for sovereigns, the twin burial chambers, and a matching account in the Nihon Shoki, though it has not been formally confirmed.
- Why is the mound such a bright white?
- It is not painted. The surface is faced with pale tuff stone, reconstructed in 2022 to follow the excavated evidence for how the original mound was clad. The aim is to show how the tomb looked when it was newly built.
- What does the octagonal shape mean?
- Eight-sided mounds appear only at the very end of the kofun era and are linked to the imperial line. The shape is one of the main reasons Kengoshizuka is connected to an empress.
- Can I go inside the stone chambers?
- General visitors view the chambers from outside the gates at no cost. Closer access is possible through guided viewings arranged in advance with the local tourist association.
- How do I get there?
- It is about a ten-minute walk west of Asuka Station on the Kintetsu Yoshino Line. There is no parking at the site, so drivers use the Asuka roadside station or Agri Station nearby.
Basic Information
| Name | Kengoshizuka Kofun and Koshizuka Gomon Kofun |
|---|---|
| Location | Oaza Koshi, Asuka Village, Takaichi District, Nara Prefecture |
| Designation | National Historic Site |
| Designation history | Kengoshizuka designated in 1923; renamed and expanded to include Koshizuka Gomon in 2014; further addition in 2015 |
| Period | Terminal Kofun period, latter half of the 7th century |
| Designated area | About 12,381.9 square meters |
| Kengoshizuka form | Octagonal mound, about 22 m across opposite faces, at least 4.5 m high |
| Access | About a 10-minute walk west of Asuka Station, Kintetsu Yoshino Line |
| Admission | Free; grounds open at all hours (special chamber viewing by reservation) |
References
- National Designated Cultural Properties Database, Agency for Cultural Affairs
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/1945
- Asuka Village Official Website
- https://www.asukamura.jp/gyosei_bunkazai_shitei_2.html
- Tabisuru Asuka Net, Asuka Village Tourism Portal
- https://asukamura.com/topics/3685/
- Museum of the Nara Prefectural Kashihara Archaeological Institute
- https://www.kashikoken.jp/museum/yamatonoiseki/asuka-nara/2018_kengoshizuka.html
Last verified: 2026.05.28