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Tomio Maruyama Tumulus: Serpentine Sword and Shield-Shaped Mirror of Exceptional Quality Discovered in Nara

Both the sword and mirror excavated at Tomio Maruyama Tumulus are regarded as Japanese masterpieces of national treasure class from the early Kofun period.



Tomio Maruyama Tumulus
A serpentine sword was excavated from the clay mound of Tomio Maruyama Tumulus. A shield-shaped mirror with a dragon pattern was also found under the sword. December 5, 2022 (provided by the Nara City Board of Education).

A bronze mirror in the shape of a shield decorated with exquisite patterns and a dako (serpentine) sword with a curved blade were excavated from a tomb in the Tomio Maruyama Tumulus (dated to the late 4th century). Located in Nara City, this is Japan’s largest circular burial mound. 

The Nara Board of Education and the Nara Prefectural Archaeological Institute of Kashihara announced these discoveries on January 25. Since ancient Japanese bronze mirrors are usually round, the shield-shaped one is unprecedented. 

The serpentine sword is an unwieldy 237 cm long. This makes it Japan’s largest iron sword excavated from an ancient burial mound. 

Both the sword and shield shaped mirror are believed to have been created in Japan and are regarded as masterpieces of national treasure-class metallurgical objects from the early Kofun period. Importantly, this discovery demonstrates a high level of metallurgy for the period.

Researchers Marvel at the Technology

Tomio Maruyama Tumulus
Tomio Maruyama Tumulus

The city’s board of education has been excavating the Tomio Maruyama Tumulus since FY 2018. In addition, it is working to get the mound classified as a national historic site. The circular mound is three-tiered. 

In late October 2022, a clay-packed burial chamber was found in the upper section of its three-tiered "tsukuridashi," a projected structure in the middle section of some kofun burial mounds. The space is about 6.4 meters long and 1.2 meters wide, with a wooden coffin buried inside. 

Then, at the end of November, a shield-shaped bronze mirror was excavated from the clay covering the wooden coffin. Thereafter a serpentine sword was retrieved from an upper section of the clay.

Tomio Maruyama Tumulus
A shield-shaped bronze mirror with a circular dragon pattern was excavated from the Tomio Maruyama burial mound. The X-ray photograph shows the pattern. (Provided by the Archaeological Institute of Kashihara)

Tomio Maruyama Tumulus Sword and Shield

The first-ever excavated shield-shaped bronze mirror is 64 cm long, 31 cm wide, and 0.5 cm thick. It features a protruding knob in the center of the back of the mirror. In addition, a circular patterned "daryumon" design is placed on both ends of the mirror, above and below the knob. The daryumon design is said to have been created in Japan to represent a mythical, sacred beast that looks like a dragon. 

Because of this design motif, experts have named the mirror a "daryumon shield-shaped mirror." In terms of other features, the mirror also has a triangular saw-tooth-patterned rim. Comprising a thin plate with a polished mirror surface, the mirror demonstrates advanced techniques. Since its discovery, it has been praised as a masterpiece of bronze work.


Based on traces of the hilt and scabbard, the serpentine Japanese sword can be reconstructed to 267 centimeters in total length. That includes its armor. 

In other words, the length of the iron sword is much longer than that of the 115-centimeter-long sword found in Hiroshima City’s Nakaoda burial mound No. 2. Of the 85 known examples of serpentine swords excavated in Japan, this is the largest and oldest.

Tomio Maruyama Tumulus
Tomio Maruyama Burial Mound on January 22. (© Sankei by Takanobu Sawano)

Exciting Finds Bring Scholars and Public 

For a few hours on each January 28 and January 29, the public was welcomed to the excavation site. However, the serpentine sword and the shield-shaped bronze mirror were not shown in these public exhibits. Instead, they were removed to the Archaeological Institute of Kashihara for preservation work.

According to Professor Seigo Wada, Director of the Hyogo Prefectural Museum of Archeology, the shield-shaped bronze mirror, with its skillful design, and the dako (serpentine) sword, "the largest of its kind in Japan," are regarded as worthy of national treasure status. 

In comparison ot other finds, the metalwork applied in these artifacts is such a high level as to astonish researchers. Indeed, one may wonder who was buried here. This discovery is expected to help provide new clues in the quest to find answers. And also to unlock the significance of the giant, round Tomio Maruyama Tumulus.

"In any event, I was astonished at the length of the sword. How did the swordsmith forge it?" asked Riku Murase. He is the curator in charge of the excavation site for the Nara Board of Education. As his comment revealed, he was awed by the discovery of the extraordinary items found in the burial mound. 

After announcing the Tomio Maruyama Tumulus discovery, researchers visited the site to inspect the excavated artifacts with great enthusiasm. They were amazed by the matchless sword and bronze shield-mirror uncovered at the site. The burial accessories provoke questions about the intended meaning and technology behind them.

Tomio Maruyama Tumulus
Archeologists discovered a serpentine sword and bronze shield shaped mirror in this burial chamber of the Tomio Maruyama Tumulus in Nara City. (© Sankei by Takanobu Sawano)

Who is the Central Interred Dignitary of the Giant Round Burial Mound?

"It is a marvel to witness the technical ability that emerged to create this exceptional design that fuses a shield and a mirror. The artist likely wanted to keep evil away from the deceased by yielding a stronger power," Dr Shinya Fukunaga explains. 

"What makes this relic even more unique is that it was created with an aesthetic aspect in mind." The specialist in archeology is a professor at the Graduate School of Osaka University.

According to Dr Fukunaga, this shield-shaped bronze mirror demonstrates high-level craftsmanship. It is only 0.5 cm thick at its thickest section and is decorated with intricate patterns. He believes these qualities suggest that there was a group of highly skilled craftsmen in the community at the time of the burial.

Tomio Maruyama Tumulus

Following an Important 1972 Discovery

In 1972, researchers for the Nara Board of Education found another clay burial chamber at the top of this tumulus. Researchers believe the tomb probably belongs to an individual of primary importance. In contrast,the newest excavated burial chamber is believed to be for a person of second rank.

Explaining, Naohiro Toyoshima, professor of archaeology at Nara University says, "The serpentine dako sword and shield-shaped bronze mirror are both magical objects. Thus, the interred person probably supported the superior figure through his knowledge of military affairs and rituals."

However, there is a view that the entire tumulus should be considered. "Since the excavated objects were not placed in the coffin, there is room to doubt whether they belonged to the person originally buried there," argues Kosaku Okabayashi, deputy director of the Archaeological Institute of Kashihara.

The Tomio Maruyama Tumulus is located some distance from other nearby mound tombs. Moreover, it is at a strategic point of transportation connecting Osaka and Nara. What kind of person would burial at this location be suitable?

Tomio Maruyama Tumulus
A shield-shaped bronze mirror was excavated from the Tomio Maruyama Tumulus and revealed on January 20, Kashihara City, Nara Prefecture (© Sankei by Yui Sutani)

Expert Opinions on the Tomb's Influential Occupant

Professor Wada shares his thoughts upon looking at the geographical location of the Tomio Maruyama Tumulus. He says, "It is closely related to the Saki mound tombs (to the northeast of the Tomio Maruyama Tumulus). Ancient tombs were built in important locations because they were closely linked to military affairs." 

On that basis, the Hyogo Prefectural Museum of Archeology director speculates, the buried person in the Tomio Maruyama tomb was "probably an influential figure at the core of the Yamato kingdom."

Dr Fukunaga observes, "The Tomio Maruyama burial mound is transitional in time and geographically when examining the shifting centers of royal authorities from northern Nara to Osaka and Kawachi." The Osaka University professor also surmises that the Tomio Maruyama Tumulus belongs to a politically powerful figure who "was close to the Yamato rulers of the time and managed the royal workshop." The person buried in the protruding section might have been a close confidant who managed the family assets.

Tomio Maruyama Tumulus
Excavation site of the Tomio Maruyama Burial Mound opened to the public on January 28, Nara City (© Sankei by Miyako Nagumo)

Possible Connection to Japan's Imperial History

Some researchers have another view. Kazuhiro Tatsumi, former professor at Doshisha University specializing in Japan’s ancient history, is one such scholar. He says: 

The fact that the Tomio Maruyama Tumulus is round rather than keyhole-shaped is significant because the keyhole-shaped burial mound is symbolic of the Yamato kingdom. This round tomb suggests the presence of another powerful clan. 

He continues explaining his theory by referring to Nagasunehiko (Tomino Nagasunebiko), a mythological aristocrat whose stories are told in the Kojiki, Japan’s ancient chronicles. In the stories, Nagasundehiko tries to prevent Emperor Jimmu from entering the Yamato region. Referring to the tomb, Professor Tatsumi adds, "this aristocratic figure may have been the source of the Nagasunehiko legend."

About the Tomio Maruyama Tumulus

Tomio Maruyama Tumulus is Japan's largest round burial mound. It is located on the west side of Tomio River in the western part of Nara City. Built in the late 4th century and constructed in three levels, it has a diameter of about 109 meters. A survey conducted by the Nara Board of Education in 1972 confirmed the presence of a clay burial chamber at the top of the mound. Burial objects stolen from the burial chamber in the Meiji period (1868-1912) are now in the Kyoto National Museum collection. They are designated important cultural properties.



(Read the related article in Japanese.)

Author: The Sankei Shimbun

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