The government’s decision in late July to nominate a group of 49 ancient burial sites in southern Osaka Prefecture for UNESCO World Heritage status has raised local hopes for a major boost in international prestige and tourism appeal.

But the move also raises sometimes politically sensitive questions about what the sites, called kofun, really are, who are buried within, and how to explain their history and meaning.

The nominated sites are known as the Mozu-Furuichi Kofun Group. They lie in two areas, in the city of Sakai just south of the city of Osaka along the coast of Osaka Bay, and in Fujiidera and Habikino in the southeast part of the prefecture. They include the 486-meter Nintoku-tenno-ryo (Nintoku Mausoleum) kofun, one of the world’s largest burial mounds.

The Mozu-Furuichi kofun are believed to have been built from the late fourth to late fifth and early sixth centuries, during the Kofun Period, which lasted for about 400 years beginning in the second half of the third century. Kofun are found over much of Honshu and Kyushu and were built in many different shapes, including keyhole, square and circular shapes. Sizes range from 10 meters to over 400 meters.

Kofun also had slightly different designs. Some were surrounded by only one moat, while others had two or three. Burial mounds might have one, two or three tiers.

The generally accepted historical explanation for the kofun mounds is that, as Japan’s ancient Yayoi culture was based on wet rice farming, settlements around rice paddies grew, and with them, local political structures known as kuni (today’s word for “country”) arose. It was these local groups that began constructing kofun.

But for whom? History and legend are mixed. The Imperial Household Agency has designated 895 sites from Yamagata to Kagoshima prefectures as Imperial mausoleums and tombs, including 188 burial mounds for senior members of the Imperial family. Citing a need to preserve the “serenity and dignity” of the tombs, entrance by the general public is forbidden and access by archaeologists is severely restricted.

In December 2014, the agency offered a guided tour to academics and reporters around a previously off-limits kofun called Tannowa Nisanzai in the far south of Osaka Prefecture, not part of the Mozu-Furuichi Kofun Group. While the Imperial Household Agency officially classifies it as an Imperial grave, some archaeologists believe it was built for a local chieftain.

Getting the tombs designated as a World Heritage site would likely lead to increased international interest in who, exactly, is buried in them.

It could also increase calls among archaeologists in Japan and abroad for better and more frequent access to carry out scientific studies on their contents, possibly leading to controversial discoveries and conclusions that would rewrite current official history.

For its part, Osaka Prefecture was careful in explaining the kofun in its English-language materials. Brochures and the English-language website promoting the Mozu-Furuichi Kofun Group introduce kofun in general as places where “people of high rank, that is the elite, in those days were buried in kofun tombs. Many powerful rulers, such as (the) great kings of the Yamato Government, had this type of mound constructed.”

In the case of the Mozu-Furuichi Kofun Group, the explanation in one brochure is that it “is considered to be the tomb group where tombs for the ruling elites, including great kings and their vassals, were concentrated. It is said that the differences in the scale and form of mounds as well as the structure of burial facilities depend on the social status and family background of the deceased, representing the sociopolitical hierarchy of the time.”

In many kofun of the Mozu-Furuichi Group, burial goods similar to those found in other parts of Asia, such as earthenware figures known as haniwa, bronze accessories and weapons have been excavated over the centuries.

“These excavated artifacts show the influence of the Korean Peninsula and China, proving that Japan had active exchanges with other East Asian countries at that time,” the brochure reads. The English-language website for the Mozu-Furuichi Kofun Group goes further, saying they could be seen “as a collection of tombs of the Kings of Wa over seven generations, together with their family members and vassals. As such, they could rightly be called the ‘Royal Tumulus Complex.’ “

Announcing its decision that the Mozu-Furuichi Kofun Group had been selected as Japan’s World Heritage candidate for the current fiscal year, the Cultural Affairs Agency explained its choice by saying the group is centered on Nintoku-tenno-ryo, the largest keyhole-shaped kofun in the country, considered to be the grave of an ancient Japanese king, and that the group includes many kofun of different sizes and designs, thus representative of others around Japan.

There are seven giant keyhole-shaped kofun in the group, with five having a double or triple moat. They are thought to have been built by ancient sovereigns who were later known as tennō (emperors), the official Mozu-Furuichi Kofun Group website reads, adding there was plenty of evidence to suggest that these seven kofun are the tombs of ancient Japanese sovereigns.

The agency also said its decision to nominate the Mozu-Furuichi Kofun Group was partially based on the belief that there was room to revise the details of the bid to reflect post-selection judgments and recommendations, although what those might be were not spelled out.

Asked about revisions to the bid, Osaka Gov. Ichiro Matsui said the recommendations and concerns of the agency need to be resolved. But now that the Mozu-Furuichi Kofun Group is Japan’s official candidate, attention is turning to what needs to be done to ensure that the group meets UNESCO’s requirements to become a World Heritage site.

“In the end, because it’s UNESCO that directs World Heritage sites, we have to get the structure of a bid past their eyes,” Matsui added.

To win its approval, UNSECO asks a number of questions about the proposed site’s uniqueness, creativity, connection to living events and traditions, and structural integrity. But what’s most important, the prefecture says, is value.

“To get on the World Heritage list, the candidate site must be of ‘Outstanding Universal Value,’ and meet certain criteria. A detailed written history of the site is less important to getting on the list than proving it has value,” said Hiroshi Yamagami, an Osaka prefectural official involved with the bid.

Yamagami said the plan was for a provisional bid to be sent by the central government to UNESCO this autumn. The final, official bid documents would be submitted to the U.N. agency by January.

“After that, representatives from the International Council on Monuments and Sites, which advises the World Heritage Committee, would visit in the summer and early autumn of 2018. They’d deliver their report on the Mozu-Furuichi Kofun Group in 2019, and the final decision to grant or reject World Heritage status would come from UNESCO around the summer of that same year,” Yamagami said.

For Sakai, getting the Mozu-area kofun listed is expected to lead to an economic windfall. A city estimate says the economic impact could be ¥100 billion for Osaka Prefecture, including about ¥33.8 billion for Sakai, mostly in the form of increased visitors. However, Sakai Mayor Osami Takeyama is also worried about how, exactly, to explain what visitors are seeing.

“Presentation (of the kofun) is becoming an issue. How do we present the kofun in the information center in a way that is convincing to those who have come?” asked the mayor in early August.

That question is likely to be answered over the coming weeks as Matsui, Takeyama and the prefectural government consult Diet members, the Cultural Affairs Agency and the Imperial Household Agency on what the final recommendation to UNESCO will look like. Given the sensitivities involved, what UNESCO officials are handed in January could make very interesting, and possibly controversial, reading indeed.