Several months ago, archaeologists in Japan discovered that a large mound in the village of Asuka in Nara Prefecture contains a pyramid-shaped tomb underneath. According to a report in the Japan Times , the tomb has preliminarily been dated to the latter half of the sixth century. The finding adds to the mystery in Asuka, where multiple carved granite stones in peculiar shapes are dotted across the region, including the most well-known structure - the Rock Ship of Masuda .

Experts at the municipal education board and Kansai University’s Archaeological Research Institute said that the recently discovered pyramid-like burial, which has been named the Miyakozuka tomb, is a terraced pyramid made of multiple stone layers. So far, researchers have excavated stepped layers made of stones packed with soil on three sides of the mound. Based on the height of the mound, it is believed that the tomb consists of seven or eight stone layers.

New excavations reveal that the ancient tomb in Japan apparently had a step-pyramid shape. Credit: Asuka Mura Public Office

The pyramid-shaped tomb is buried under an earthen mound, which is up to 7 metres in height and 40 metres in length. Experts say the structure is similar to those found in the ancient kingdom of Koguryo (3 rd century BC – 7 th century AD), which reigned over north-eastern China and the northern part of the Korean Peninsula.

The village of Asuka is also known to be an ancient land with historical interest. It has its origins in the Tumulus Period (250-552 AD), also called Kofun jidai, which means Old Mound period. This era of Japanese history is characterised by a particular type of burial mound that was popular at the time; specifically key shaped earthen mounds surrounded by moats. However, the newly-discovered step pyramid is quite different to those that have already been found.

The Miyakozuka Tomb in Asuka, Nara Prefecture, as seen from a helicopter. Credit: Masaki Yamamoto

While archaeologists have not yet identified the tomb’s owner, one hypothesis is that it belongs to Soga no Iname, a Yamato Dynasty leader who died in 570 AD. Soga no Iname was a statesman who acquired great power from his control of immigrants from China and the Korean Peninsula, who brought cultural and technological advances with them to Japan. He had close ties to the Koguryo kingdom, so the architectural design of his tomb may have been influenced by the tombs associated with that kingdom.

Artist’s rendition of the Miyakozuka pyramid-shaped tomb. Credit: The Asahi Shimbun

The village of Asuka is known for many megalithic discoveries, including the Ishibutai tomb believed to have been built in the seventh century for Soga no Umako, a son of Iname who died in 626.

The largest and most enigmatic of the carved stones in Asuka is the Masuda-no-iwafune (the 'Rock Ship of Masuda' ). The stone carving, which stands near the top of a hill in Asuka, is 11 metres in length, 8 metres in width and 4.7 metres in height, and weighs approximately 800 tonnes. The top of has been completely flattened and there are two one-meter square holes carved into it and a ridge line that is parallel to both holes. At the base of the stone are lattice-shaped indentations which are believed to be related to the process that was used by the builders to flatten the sides of the rock.

The Masuda no Iwafune (the ‘Rock Ship of Masuda’). Credit: asuka-park.go.jp

Numerous suggestions have been put forward to account for this unique structure. It has been suggested that the stone was carved in commemoration of the building of Masuda Lake, which was once located nearby (now drained and part of Kashiwara City), hence the name ‘rock ship’. However, others have suggested it was an unfinished tomb, or an astronomical observation point. The ridge line across the top of the rock runs parallel to the mountain ridge in Asuka and lines up with the sunset on a certain day of the year called "spring doyou entry", which was important in the lunar calendar and for early Japanese agriculture as it signalled the beginning of the agricultural season.

Very little is known about the Masuda no iwafune stone carving, as well as other megalithic structures and constructions in the region of Asuka. While it is hoped that further excavations may give up some of the secrets, in the end, the origin and purpose of these enigmatic features of ancient Japan may be lost to the pages of history.

Featured image: Artist’s rendition of the Miyakozuka pyramid-shaped tomb. Credit: Yomiuri Shimbun

By April Holloway