Hidden chamber found within a 5th century burial mound

Archaeologists discovered a hidden chamber in the late 5th-century Inariyama burial mound in Gyoda, Saitama Prefecture, Japan. Experts wonder who was buried inside.

The burial mound (by Asahi Shimbun)

The 120-meter-long burial mound, dated to the 5-th century, was excavated in 1968. The excavations resulted in a discovery of a chamber encased with clay and another one, a burial chamber made of small rocks, containing a bronze mirror and 73.5-centimeter-long sword blade with a gold-inlaid inscription. The blade was called Kinsakumei tekken and is considered a national treasure in Japan, believed to be among the oldest examples of Japanese script in the country.

Situation map of the site (by Asahi Shimbun)

The characters on the sword only came to light in 1978 after the artefact underwent X-ray imaging. The inscription states that the sword was made in 471 by an individual named Wowake who served King Wakatakeru as the head of his royal guard. The king is identified with the Emperor Yuryaku ruling in the 5th. Now, the keyhole-shaped tumulus was studied by experts from Tohoku University with ground penetrating radar (GPR) technology.

Burial chamber within the mound (by Asahi Shimbun)

The mound is believed to have been originally encircled by a moat and was the resting place of a very high ranking individual. The owner of the sword was assumed to have been buried in the mound but the recent results indicate that there might be a different case. It seems that the discovery of another chamber deeper underground might suggest that the mound was built for someone else.

3D visualisation of non-invasive measurements showing a lens-like structure underground (by Asahi Shimbun)

The non-invasive survey of the site revealed a lens-shaped structure 4 meters long and 3 meters wide, with a maximum thickness of 1 meter. The chamber lies about 2.5 meters below the surface. There also appears to be a part extending beyond the researched area. This new chamber is thought to be the original burial site and the previously found small rock and clay chambers, located nearby, are considered to have been created for later generations.

Non-invasive research at the site (by Asahi Shimbun)

(after Asahi Shimbun, Eiichi Miyashiro & Takuya Kawasaki)

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