The archaeologists weren't allowed to excavate, but they did find previously unknown terra cotta haniwa figures on the tomb's eastern side. These funerary statues were believed to help tend to the elite after death.
In addition to overseeing Jingu's tomb, the Imperial Household Agency looks after some 896 sites said to contain the remains of imperial family members.
Of those, around 70 are kofun tombs dating to before the seventh century. These keyhole-shaped mounds surrounded by moats are some of the largest and most historically important burial sites in Japan.
"It was during the Kofun period [in the third to seventh centuries A.D.] that the Japanese nation was established on the Japanese archipelago," Takahashi said.
"The tombs hold the key to unlocking details of the Kofun period."
While the Imperial Household Agency shares the results of its research, the agency has been reluctant to give independent archaeologists access.
In a fax to National Geographic News, the Imperial Household Agency's Tombs and Mausolea Division wrote: "Imperial Household religious ceremonies continue to take place at tombs and mausolea. As they are objects of remembrance and veneration for the public and imperial family, preserving their peace and dignity is of paramount importance."
The agency added that although they will consider further research requests, "excavation is not permitted."
Takahashi, however, believes the agency is reluctant because excavation might threaten bureaucrats' control over the tombs.
Of the oldest, most significant tombs under the agency's jurisdiction, very few can realistically be proven to contain the remains of imperial family members, he said.
Nevertheless, the status of the tombs is all but set in stone. The last time that the agency changed an imperial tomb's designation was in 1881.
Other experts have suggested that the hesitation is because courtiers and conservatives fear excavation will uncover blood ties between the supposedly pure Japanese imperial line and the Asian mainland, specifically Korea.
But Walter Edwards, professor of Japanese studies at Tenri University in Nara, argues that the "Korean bones" issue is a red herring.
"Blood links between Korea and the Japanese imperial family are documented from the eighth century," he said.
"Even the current emperor [Akihito] has said that he has Korean ancestry." Edwards suggests that the agency's attitude has more to do with trying to maintain the imperial family's dignity.
But faced with the costs of keeping up hundreds of sites, the reputedly cash-strapped Imperial Household Agency may eventually allow more access as a way to get more public funds, he suggested.
The agency may now try to handle the tombs as both national heritage sites and as private graves of the imperial family.
"The problem is how to strike a balance between the two," Edwards said.
In the meantime, high on archaeologists' wish list for access is the fifth-century tomb of Emperor Nintoku in Osaka Prefecture.
In the past the agency has refused access to the tomb on the grounds that the boat to cross its moat is too old and unsafe.
At 1,594 feet (486 meters) long, the mausoleum is the largest in Japan.
"[It is] almost as large as the biggest of the Great Pyramids [of Egypt] in volume," Edwards said, "and like the latter it is a truly monumental work from the ancient period."
SOURCES AND RELATED WEB SITES