An extraordinary sword unearthed from the Tomiomaruyama Kofun burial mound in Japan has astonished archaeologists with its unprecedented length and unique design, blending features of both the single-edged katana and double-edged swords.

On March 26, Mainichi reported that the Kashihara Archaeological Institute in Nara Prefecture, alongside the Nara City Board of Education, officially announced the discovery of the colossal “dako” iron sword. This artifact, uncovered from Japan’s largest burial mound located in Nara City, is believed to be the origin of ceremonial swords created under the control of the Yamato monarchy.

The dako sword measures an impressive 2.37 meters in length and 6 centimeters in width, making it the longest iron sword from the Kofun period (circa 3rd to 7th century) found in East Asia. It was discovered in December 2022 alongside a shield-shaped bronze mirror from an unexcavated burial site within the Tomiomaruyama Kofun mound, dating back to the late 4th century and measuring 109 meters in diameter.

During preservation, the archaeological institute carefully removed dirt from the sword’s surface and meticulously examined the artifact. Due to over 1,600 years of burial since the late 4th century, the sword’s scabbard was almost entirely reconstructed at the time of excavation.

It was found that the hybrid blade had been bent six times, with a total measured length of 2.85 meters when fitted with its hilt and scabbard. The scabbard, made of Japanese bigleaf magnolia wood, measured 2.48 meters.

Masaki Kanekata, head of the archaeological institute, expressed amazement at the recent discoveries, emphasizing their significance in understanding the ceremonial use of swords by the Yamato monarchy. Naohiro Toyoshima, a professor of archaeology at Nara University and an expert in ancient swords, remarked that the innovative design of these iron blades likely began with this 4th-century sword, marking a turning point that led to distinct designs for single and double-edged swords by the 5th century.

Kosaku Okabayashi, deputy director of the Kashihara Archaeological Institute, noted that these findings demonstrate the advanced technology of the Kofun period, far beyond previous assumptions. The newly unearthed sword and bronze mirror are considered masterpieces of metalwork from that era.

The giant dako sword was on public display at the Kashihara Archaeological Museum in Nara Prefecture until April 7.