Outlines of Iwase-senzuka


a burial mound
Section Maeyama A

"Special Historic Sites"

Iwase-senzuka is one of National Special Historic Sites of Japan.

According to Agency for Cultural Affairs of the national government, 1,895 sites are currently designated as Historic Sites, and among Historic Sites, particularly important 63 sites are classified as Special Historic Sites.

The Golden Pavilion and Himeji Castle, for example, are also in the same category.


newly-found kofun
newly-found kofun

A large number of kofun are located inside the area of Iwase-senzuka. The number is said to be 900. I have learned that Iwase-senzuka is one of the largest kofun clusters in Japan. In addition, and the total might increase in the future. Burial mounds could be newly detected there. Actually, four burial stone chambers were recently found near the museum in 2022.

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"The 6th Century"

I have learned about Iwase-senzuka as follows:

  • Many of clustered kofun in Japan appeared in the late Kofun Period, roughly in the 6th century. Iwase-senzuka is one of them.
  • Some Iwase-senzuka kofun appeared in and after the late 4th century. The large majority, however, were constructed in the 6th century.
  • During the early and mid-Kofun Period, only the highest-ranking people had their own kofun. Then, in the late Kofun Period, those who had never been permitted to possess their own kofun before commenced to build their own kofun.

The social circumstances must have changed at the beginning of the late Kofun Period in the early 6th century.

"Iwase-type Horizontal Burial Stone Chambers"

Unique structure made of distinctive stones characterizes burial facilities in Iwase-senzuka. A word "Iwase-type" describes the type. The manner differs in its chamber shape, material, the construction method, and others. The approach is never found even in nearby areas including Osaka and Nara. The method is employed only in the northern part of Wakayama Prefecture.

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Iwase-senzuka Kofun Cluster

the Tomb Owners

Nichizen-gu Shrine
Nichizen-gu Shrine

Iwase-senzuka is thought to have been closely related with the Ki family, a dominating family at the mouth of the Kinokawa River in Kofun Period.

The Ki(i) family members have taken over the position of the chief priest of Nichizen-gu Shinto Shrine since ancient times.

Many of kofun at Iwase-senzuka were built in the 6th century. The tomb owners are thought to have been both the Kii family members and those who supported the family.

Sections in the Area of Iwase-senzuka

The large area of Iwase-senzuka is usually divided into 10 sections: Hanayama, Otani-yama, Dainichi-yama, Iwase Mae-yama B, Iwase Mae-yama A, Wasa, Imbe Mae-yama, Imbe, Terauchi and Sando.

The area designated as Special Historic Sites includes Otani-yama, Dainichi-yama, Iwase Maeyama B, Iwase Mae-yama A and a part of Wasa (Tenno-zuka Kofun).

Dainichi-yama No.35
Dainichi-yama No.35

The Period When the kofun were Built

On the whole, kofun at Iwase-senzuka are thought to have been built between the end of the 4th century and the beginning of the 7th century.

However, it is thought that the periods when kofun were frequently built were different from place to place.

For instance, while kofun in Iwase Mae-yama A were built between the mid 5th century and the end of the 6th century, those in Dainichi-yama were built only in the first half and the middle of the 6th century.

Sizes of Kofun at Iwase-senzuka

Iwase-senzuka has two large keyhole-shaped kofun. They are Dainichi-yama No.35 and Tenno-zuka. Both are 86 meters long. The largest round kofun at Iwase-senzuka has a diameter of around 40 meters (Terauchi No.57) .

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Burial Stone Chambers at Iwase-senzuka

box-style stone coffin
Maeyama A No.100 (Box-style)

Four Styles Found at Iwase-senzuka

Styles of burial facilities varied richly even only in the Kofun Period as mentioned below.

Wooden Coffins Coated with Clay
This old style is also found at Iwase-senzuka.
Box-style Stone Coffins
This style did not have a burial stone chamber.
Vertical Burial Stone Chambers
The space for the dead became large enough to be called "chamber". Only one person was enshrined there. The style was popular in the 5th century.
Maeyama A No.47
Maeyama A No.47 (Vertical one)
Horizontal Burial Stone Chamber
A horizontal passage was attached to the burial chamber. It became possible to enshrine plural people when necessary. The chamber was closed with a door-like rock. The style appeared in the northern part of Kyushu in the 5th century and grew popular in other places in the 6th century.

Burial Stone Chambers Visitors Can Enter

As a matter of course, all the burial stone chambers which you can walk in at Iwase-senzuka are horizontal stone chambers. Vertical ones are too small to enter.

Iwase-senzuka has several burial stone chambers you can walk in. They are always open to visitors for free. Many of them are located in a section called Iwase Maeyama A, which is the closest to the museum building.

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Iwase-type Horizontal Burial Stone Chambers

The manner of the horizontal burial stone chambers at Iwase-senzuka is quite different from others. The differences lie in construction materials, wall structure, space for the dead to be laid, and others.

Materials Used at Iwase-senzuka

The building materials used at Iwase-senzuka are exclusively crystalline shists. It is a kind of metamorphic rock which can be split into thin layers. They are processed into flat boards like bricks and piled up to form walls. Mortar-like materials, however, are not used at all at Iwase-senzuka.

Crystalline shists are easy to find in the park area of Iwase-senzuka. The outcrops are seen in different places along the walking course.

slightly-slanted walls
slightly-slanted walls

Slanted Walls

Relatively thins plates of crystalline shists are piled up by corbeling to form a slightly-slanted interior walls.

Stone Beams and Stone Shelves

The horizontal rock components also attract visitors' attention. Stone beams and stone shelves are thought to strengthen the structure of the chambers. Actually, almost all the stone rooms have kept their original shapes for around 1,500 years.

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No Coffins

pebbles on the floor
pebbles in Maeyama A No.46

Coffins are found in horizontal burial stone chambers of the Kinai area including Nara and Osaka. However, no parts of coffins have been identified in Iwase-senzuka.

It is interesting to know that stone coffins were not seen inside some stone chambers in the northern part of Kyushu, either. Relationships between the Ki family in Wakayama and Northern Kyushu might have existed in the Kofun Period.

Advanced Techniques

Soem various advanced methods of building stone chambers are seen at Iwase-senzuka. The way to keep the floor clean is one of them. Pebbles from riverbanks are laid over the ground. I hear that drainage ditches are installed under the pebble flooring in many cases.

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