We have already mentioned the imposing keyhole-shaped imperial burial mound of Daisen "
kofun" in Sakai, Osaka Prefecture,
in this thread.
The Imperial Household Agency, which had previously imposed strict limitations on access, oversees the Daisen
kofun burial mound, formally recognized as the Emperor Nintoku Mausoleum. This ancient, forested mound is the largest of 49 sites inscribed on UNESCO's World Heritage list in 2019. The burial sites date back to the late fourth to late fifth centuries, often regarded as the "golden age" of burial mounds.
The Daisen "kofun" burial mound in Sakai (photo credit: Ito Shinnosuke)
On 7 March, agency officials accompanied representatives from 17 historical and archaeological academic organizations to the site, marking the first time in the postwar period that scholars were permitted entry. Since the mound spans 486 metres and is encircled by a moat, the group had to travel to the structure by boat. Once there, they spent roughly two hours exploring 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 had long been eager to study the Nintoku tomb. Still, the Imperial Household Agency had only granted access to 17 other sites before this. The academic group expressed their intention to continue urging the agency to increase the frequency and scope of observation visits and eventually open the site to the public.
Although the agency designates the Daisen burial mound as Emperor Nintoku's mausoleum, no definitive evidence has confirmed the identity of the individual buried there. The mound dates back to the fifth century. While local authorities examined its front section in 1872, access was subsequently restricted.
Joint excavations by the Imperial Household Agency and the Sakai municipal government in 2018 and 2021 revealed cylindrical
haniwa — terracotta figures and funerary objects — along with stone decorations on the embankments. However, the burial chamber itself remained untouched.
I asked ChatGPT why the Imperial Household Agency is so restrictive in granting access to those kofun:
The debate around Japan's kofun tombs is fascinating and controversial. Scholars have long pushed for more access to these ancient burial mounds, arguing that archaeological research could uncover invaluable insights into Japan's early history, the origins of the imperial family, and the country's connections to the Asian continent. However, the Imperial Household Agency (IHA) remains deeply cautious, caught between tradition, historical narratives, and concerns over disturbing sacred spaces.
One central point of contention is the identity of those buried in the tombs. The Daisen kofun, for example, is said to house Emperor Nintoku, but there's no solid archaeological evidence to confirm this. If investigations were to reveal that the tomb's occupant wasn't an emperor, it could challenge the official narrative of Japan's imperial lineage — something the IHA seems keen to avoid. The imperial family's legitimacy is historically tied to claims of an unbroken bloodline stretching back to the sun goddess Amaterasu, so any discovery that undermines this could be politically sensitive.
There's also a fear of international scrutiny. If full-scale excavations revealed evidence of outside influence — say, from Korea or China — it might complicate nationalistic narratives of Japan's purely indigenous development. Some historians believe kofun culture was influenced by migration and cultural exchange with the Korean peninsula, but without access to burial chambers, it isn't easy to confirm.
Another factor is the spiritual and cultural significance of these sites. In Shinto beliefs, ancestors and nature are deeply intertwined, and disturbing the final resting place of an emperor could be seen as disrupting the connection between the imperial family and the divine. The IHA treats the kofun not just as historical monuments but as living sacred spaces, which adds another layer of complexity to the access debate.
In recent years, small concessions have been made. Limited scholarly visits and joint excavations of non-burial areas have taken place, and the kofun sites were added to the UNESCO World Heritage list in 2019. However, full access to burial chambers remains off-limits, and the IHA shows no sign of changing its stance completely.