Masuda-no-Iwafune (益田岩船)in NARA

【Masuda-no-Iwafune / 益田岩船】

There is a man-made object atop the mountain, with square holes made in a boulder inferred to weigh 800 tons.

【Masuda-no-Iwafune / 益田岩船】 (Rock Ship of Masuda), near the top of Iwafune hill, is the largest carved stone object in the Asuka region. It is a huge boulder inferred to weigh 800 tons, with two square holes opened on the top. Clearly worked by human hands, it is not known who made it, when, or for what purpose.
The true nature of this rock has long been debated. Various theories have emerged, such as its being equipment for ancient people’s astronomical observations, or the pedestal for stone inscriptions, but recently the most favored view is that it was abandoned in its original position in the midst of making it into a stone burial chamber. As there are fissures on the rock’s circumference, it may be that it was abandoned when these were noted during the work.

Access: about 1 km to the west or about 20 minutes on foot from Kintetsu Yoshino Line Okadera Station

Address: 8-20-1 Hakusucho, Kashiwara-shi, Nara Prefecture


Huge (11m × 8m × 5m high) rock on a hill with 2 square halls on the top and traces of scraping below. The purpose is unknown, but has some similarities with Ishi-no-Hōden (huge rock with a concave band) in Hyōgo prefecture and Kengoshi-zuka Kofun tumulus (2 chambers in 1 rock) just 500m away. Masuda-no-Iwafune and Ishi-no-Hōden might be planned to be the chamber for the Kengoshi-zuka Kofun tumulus, but abandoned for some reasons.




Kengoshizuka Kofun Tumulus(牽牛子塚古墳)

Kengoshizuka Kofun

Kengoshizuka Kofun

Kengoshizuka Kofun Tumulus is also known as Asagaozuka. 
It is located in the best location of the lower part of the Mayumi-no-oka hill where you can view the peak of the Kaibukiyama mountain (210 meters), the Mausoleum of Emperor Hinokuma and other tumuli. It has been designated as a National Historical Ruin.

It is an octagon shaped tumulus of 22 meters in total length, 4.5 meters in height. 
There are two rooms, left and right, curved to create from one large stone a stone sarcophagus with a side entrance. Its has dome-shaped ceiling and its construction is unparalled.

There are many excavation products found including coffins, some fragments of accessories, bracket decorations, glass round balls, and human bones during the excavation.

People who were buried here were believed to be Empress Kawashima-no-miko and King Asakaou, however, actual excavation proved that the buried people were Emperor Saimei and Empress Hashihito-no-himehiko. The reason why the buried people were the Emperor’s family is beause of the contruction of tumulus, the style of coffin and the direction where it is built are all related to the similarities of imperial tumuli. It is the tumulus built in the final Kofun tumulus period.

Koshitsukagomon Kofun tumulus is also found in the south east part of the stone sarcophagus with side entrance. This Koshitsukagomon Kofun tumulus is related to the Jyo in the year of Techi 6 in the “Nihon Shoki” (the oldest chronicles of Japan).

The mysterious monoliths of Asuka Nara and the Rock Ship of Masuda

The village of Asuka is located in the Takaichi District of the Nara Prefecture in Japan. Asuka is 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. One of the most unique features of Asuka is the multiple carved granite stones in peculiar shapes in various parts of the region. The largest and most unusual of the carved stones 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.

Asuka is a village nestled among the hills of the Nara Prefecture of Kansai, Japan, and Asuka is home to some seriously strange stone carvings. The village has its origins in the Tumulus Period (250-552 AD).

So what is the nature of this rock and what is its purpose? Who made it, when and why? Unfortunately, there are no definite answers to those questions, but numerous suggestions have been put forward to account for this unique and unusual structure.

In the region in which Masuda no iwafune is found, there are many Buddhist temples and shrines that may suggest the carving was made by Buddhists, perhaps for some kind of religious or ceremonial purpose. However, Masuda no iwafune does not resemble the style or construction of any other Buddhist monument.

Another suggestion comes from the name of the rock itself, which translates to ‘the rock ship of Masuda’. 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).

Masuda Lake

Masuda pond is a large reservoir built in the early An period. It is a pond that existed in Kashihara City, Nara Prefecture, and is now extinct. Kashiwara New Town was built on the site. In the early Heian period, in 822, a huge irrigation reservoir was built on the Takatori River, where a dike was built to stop the flow of water.

The popular theory of Rock Ship of Masuda is that it was used as an astronomical observation point. Evidence for this perspective comes from the ridge line across the top of the rock which 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 occurs 13 days after the sectional solar term ‘Pure Brightness’. This day was important in the lunar calendar and for early Japanese agriculture as it signalled the beginning of the agricultural season. However, this perspective has been largely dismissed by scholars who do not recognise it as an ancient astronomical observing station.

Some historians believe that the rock is just the remains of a tomb that was designed for members of the royal family. However, this does not explain the unusual features, such as the square holes on top, nor have any bodies been found. To account for this, some have suggested it was intended as the entrance of a tomb but was unfinished.

The rock ship, being the largest of the mysterious rock mounds, is 11 meters by 8 meters, by 4.5 meters high, and is made of solid granite, which makes it somewhere around 80 tons as it sits.

The “boast stone” is one of most strikingly enigmatic of the Asuka megaliths. One puzzling characteristic is that in places it is rough and unfinished, seemingly entirely like a work of nature, and in other places beautifully cut into right-angled planes..” 
“Masuda no Iwafune” does not resemble the style or construction of any other Buddhist monument and represents one of the greatest mysteries of Japan.

【阪本研究所】 SK laboratory 💠貿易業務サポート💠広告動画制作💠銘板制作販売 / 大阪府八尾市 Email ➡

【阪本研究所 SK laboratory】🌏 大阪府八尾市 
Representative:Kazuyoshi Sakamoto


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