Photo/Illutration The Daisen “kofun” burial mound in Sakai (Shinnosuke Ito)

SAKAI--Researchers got an almost unheard of chance March 7 to step foot atop an imposing keyhole-shaped imperial burial mound dating from the fifth century that still holds many secrets.

The Daisen “kofun” burial mound, known formally as the Emperor Nintoku Mausoleum, is managed by the Imperial Household Agency, which until now had severely restricted access.

The wooded burial mound is the largest of 49 sites that were included in UNESCO’s World Heritage list in 2019. The mounds were all constructed between the late fourth century and late fifth century, a period often called the “golden age” of burial mounds.

On March 7, representatives from 17 academic organizations of history and archaeology were escorted to the burial mound by Imperial Household Agency officials. It was the first time in the postwar era that scholars have been allowed to step foot on the sacred site.

The structure itself is 486 meters long and surrounded by a moat, so the group had to approach it by boat.

The members spent about two hours walking around the first level terrace.

“We found areas where the mound had fallen in and layered stones that had been redone,” said Shin Hidaka, a professor of archaeology at Tokyo Gakugei University who represented the Japanese Archaeological Association.

“Because there were areas unknown from survey maps or from observations outside the mound, we want to find a way to share the knowledge with the public.”

All of the burial mounds included in the World Heritage list are located in bustling residential areas of the cities of Sakai, Habikino and Fujiidera, all in Osaka Prefecture.

But because the mounds held the remains of emperors and other members of the imperial family, the Imperial Household Agency had banned entry.

It was only in 2008 that scholars were allowed limited access.

Scholars always had their sights set on the Nintoku tomb, and it is only the 18th that the agency has allowed to be observed by academics.

Members of the scholarly group said they would continue to press the agency to expand the range and number of observation visits, as well as open the site to the public.

Although the agency calls the Daisen burial mound the mausoleum for Emperor Nintoku, no confirmation has ever been made of who is buried there. The mound was built in the fifth century.

Local authorities studied the front part of the tomb in 1872, but access was cut off after that.

In 2018 and 2021, the Imperial Household Agency and Sakai municipal government conducted joint excavations of embankments on the mound and discovered cylindrical “haniwa,” a collective term for terracotta clay figures and funerary objects created to decorate the surface of the large mounded tombs, as well as stone decorations.

But no entry was made of the burial chamber itself.

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