Iwase-senzuka
This page aims to provide vital information related to Iwase-senzuka Kofun Cluster. The contents are divided into the next three groups.
Keywords
"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.
"900"
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.
"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.
The Kofun period
Barrows Called "Kofun" in Japan
Technical Term "Kofun"
A word "Kofun" literally means "old mounds" in Japanese. Many Japanese people use the expression in that sense in their daily lives.
When the word is mentioned in the field of history or archeology, however, it is a technical terms. The term is defined as "burial mounds constructed in the Kofun Period," and other types of burial mounds built in different periods have their own names in Japanese.
Japanese kofun Shapes
Kofun assume several different shapes. Keyhole-shape represents the appearance and followed by square-front-and-square-back ones, round ones, and square ones.
Keyhole-shaped kofun are called "zen-po-ko-en fun" in Japanese. The name literally means "front-round-and-back-square mound". The square-front-and-square-back kofun are called "zen-po-ko-ho fun". So, they may be sometimes confusing even for Japanese people.
Shapes and Sizes
I have learned a widely-accepted theory about shapes and sizes of kofun as follows:
- Shapes and sizes of kofun must have been based on the tomb owners' social rank and political power.
- It is tought that keyhole-shaped kofun were in the highest rank; front-square-and-back-square ones were in the second-highest; round ones were in the third-highest; square ones were in the fourth-highest.
- Among the same shapes, it must have been that the larger a kofun was, the stronger their political power was.
The Largest Kofun in Japan
The largest keyhole-shaped kofun in Japan is "the 486-meter-long mausoleum of Emperor Nintoku" in Sakai, Osaka Prefecture. Nintoku, the 16th emperor of Japan, is thought to have been on the throne around the end of the 4th century or the first half of 5th century if he actually existed. About 40 among 160,0000 kofun are longer than 200 meters long in Japan.
The Kofun Period in Japan
The Order of Periods
My fundamental understanding of the course of history until the Kofun Period is as follows.
- In the Old Stage Age, people inhabiting a single island (proto-Honshu) were large-sized animal hunters.
- Around 13,000 years ago, people commenced to adapt their lives to warmer natural environment. That was the beginning of the Jomon Period (the New Stone Age in the world).
- Jomon people were basically hunter-gatherers.
- Around 3,000 years ago, wet-rice cultivation was introduced to the northern part of Kyushu from the Korean Peninsula. That was the beginning of the Yayoi Period there.
- The nutritious grain increased population especially in the western part of the main islands.
- Consequently, there appeared large villages with hierarchy. The chiefs assumed command over the agricultural production, religious rituals, and the community safety.
- Those villages gradually formed small independent countries.
- In the late Yayoi Period, powerful large countries appeared, and the influential chiefs commenced to ally with each other for their common benefit (iron, etc.).
- In the mid 3rd century, kings of allied countries began constructing large keyhole-shaped kofun as the symbol of their alliance. That was the beginning of the Kofun Period.
Four Stages in the Kofun Period
Subdivisions of the Kofun Period and my understanding of their outlines are as follows. The terminal period of the Kofun period, however, overlaps with the Asuka Period.
- the early period (the mid 3rd century to the end of the 4th century
- the middle period (the end of the 4th century to the end of the 5th century)
- the late period and the terminal period (the 6th century to the 7th century)
The Early Period
- Very large keyhole-shaped kofun appeared in the Nara Basin.
- Burial facilities were vertical stone chambers.
- Grave goods were mirrors, precious stones, swords, stone products, iron farm implements, iron tools and so on.
The Middle Period
- Large-sized kofun were constructed at various spots in Japan.
- Among burial accessories, military items such as horse gear, armors and swords increased.
- Unglazed ceramic ware ("sue" in Japanese) entered production in the southern part of present Osaka Prefecture.
- Horizontal stone chambers appeared in the northern part of Kyushu.
The Late and Terminal Periods
- A large number of Horizontal stone chambers were constructed.
- Haniwa declined in the Kansai Region (including Nara, Osaka) but became more popular in the Kanto Region (near Tokyo).
- Kofun Clusters appeared in various places.
The Kofun Period in Present Wakayama City
The Kinokawa River
The city is situated at the mouth of the Kinokawa River. The first-class river runs from an area of high rainfall in the central part of the Kii Peninsula.
During the Jomon Period, earth and sand from the Kinokawa River gradually formed the Wakayama Plains, where wet-rice cultivation started and developed in the Yayoi Period.
Geographical Benefit
Two environmental benefits the Kinokawa River brought to the mouth are as follows.
- An estuary harbor inside a long sandbar functioning as a breakwater.
- Agricultural water for rice paddies.
A harbor at the mouth of the Kinokawa River
It is already known that the landform of the Kinokawa River mouth area in the ancient times was much different from that of today. In the Kofun Period, the river, which currently runs westward to the sea, bended southward due to a ridge of sand, and the present central city area was an estuary.
In 1981, remains of seven large wooden store houses constructed in the Kofun Period were discovered at Narutaki, a low hilly land near the north bank of the Kinokawa River, in Wakayama City. The archeological evidence suggests that the estuary was utilized as a harbor.
Actually, "O-no-minato", a name of a harbor, is mentioned in Record of Ancient Matters and Chronicles of Japan, which were completed in the early 8th century.
An Irrigation System
In the south bank area of the Kinokawa River, an irrigation system for rice paddies, which is called "Miyai-yosui." today, has been used for a very long time.
According to archeologists, the structure for agricultural water already existed and the Wakayama Plains was a granary in the Kofun Period.
Kofun in the North Bank Area
In the north bank area of the Kinokawa River, several keyhole-shaped kofun including very large ones in Misaki Town, Osaka Prefecture, were constructed in the 5th century. Interestingly, in the next century, clustered kofun appeared at Iwase in the south bank area.
Iwase-senzuka Kofun Cluster
the Tomb Owners
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).
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) .
Iwase-type Horizontal Burial Stone Chambers
Four Styles Found at Iwase-senzuka
Styles of burial facilities richly varied 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
The second typical type is called "box-style stone coffin." This style did not have a burial stone chamber.
Vertical Burial Stone Chambers
The third type is called "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.
Horizontal Burial Stone Chambers.
Then, a horizontal passage was attached to the burial chamber. The style is called "horizontal 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.
Photos of Accessible Burial Stone Chambers
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.
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.
No Coffins
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.