Keyhole-shaped Tumuli (前方後円墳)

A keyhole-shaped tumulus (called zenpo koen-fun in Japanese) is a form of kofun (tumuli) in Japan. The shape that combines two burial mounds, whose plane surfaces are round and square, is unique to Japan. It has been characterized for being big since it first appeared. As regards the shape, it is considered today that it was formed when the passage portion of the round tomb covered with a heap of earth developed and merged into the burial mound. Keyhole-shaped tumuli range over a wide area of the Japanese Archipelago. They extend from Oshu City of Iwate Prefecture in the north to Kagoshima Prefecture in the south. The recent investigation has confirmed that they are also present in the southwestern Korean Peninsula where there was ancient Gaya.

Zenpo' (expressed as 前方 in kanji, or Chinese characters) means that 'the front half is a square,' taking the first letters of 前半分 (the first half) and 方形 (a square). And it does not refer to 'an anterior direction' (written as 前の方向 in kanji).

The Origin

There have been some discussions concerning keyhole-shaped tumuli originating in Japan. The most famous theory is that they developed uniquely from the above-ground tombs of the Yayoi-period. According to this theory, a land bridge (or overpass) was created by leaving part of earth unexcavated when building a moat around the existing round barrow. This section developed and merged into the burial mound serving as a land bridge connecting the world of humans with a tomb (the world of death). In contrast, Sueji UMEHARA has proposed a theory arguing that it is the influence of mainland China. He claims that it originates in the altar and other things that lied anterior to the mausoleum of the first Quin Emperor, the pit filled with the Terracotta Army and the other objects.


In ancient times, keyhole-shaped tumuli were described as being gourd-shaped. The term 'front-square rear-round' (pronounced zenpo koen in Japanese) was first used in "Sanryoshi" written by a Japanese classical scholar of the Edo Period, Kunpei GAMO, in the early nineteenth century. GAMO reasoned from the name 'kurumazuka,' which is found in various places, that keyhole-shaped tumuli were modeled after a kyusha. And he argued that the square portion represents the front portion of the car. However, it is considered today that such a car did not exist in the Kofun Period. At the end of the Meiji Period, William GOWLAND conjectured that a round barrow and a square barrow were combined to form a keyhole-shaped tumulus. Likewise, Kanji KIYONO hypothesized that the main barrow and a baicho (a small barrow next to a large-scale tumulus) were joined together to give the keyhole-shape. Later, other theories emerged claiming that keyhole-shaped tumuli were copied after a shield and a jar-shaped earthen vessel.

In the present research, the rounded rear, or a mound used for a burial is considered to be the main mound. And the projecting portion, whose plane surface is shaped like a plectrum, rectangle, square, trapezoid, etc., is collectively referred to as the square front. The square front is a variation of the projecting portion of the tomb that was covered with a heap of earth from the Yayoi Period. There is an opinion that it originally emerged and developed as an altar for honoring the deceased. There is also another view that it was a route taken by a funeral procession to reach the rounded rear, where there was a tomb. It is considered that it gradually developed a unique form. However, in more recent years, burials also began to take place in the square front. Yet, the terms like keyhole-shaped tumuli, the front square, and the rounded rear are still used because of customs and convenience. The front square of older keyhole-shaped tumuli is low and shaped like a plectrum, while the rounded rear is built high and big regardless of date of construction. It is believed to have a plectrum-shape because either the right or the left ridgeline of the front square was extended to enable a funeral procession to travel on the slow sloping road.


The only places where the presence of keyhole-shaped tumuli is not determinate are three prefectures in the north, namely Hokkaido, Aomori, and Akita, and Okinawa Prefecture in the south. The period and number of construction varies. However, a few to a few hundred keyhole-shaped tumuli are known to exist in the other forty-three prefectures. They are found in isolated islands like Tsu-shima Island, Iki-no-shima Island, and Oki-shoto Islands. On the other hand, however, no keyhole-shaped tumulus has been identified in Awaji-shima Island. It has been ascertained that there is little difference among the most recently constructed keyhole-shaped tumulus in each location in terms of date of their construction. Tokushima Prefecture is one of the few exceptions, in which no keyhole-shaped tumulus has been constructed since the fifth century.

With respect to areas outside the Japanese Archipelago, the recent research by Korean archeologists has revealed presence of the keyhole-shaped tumuli that seem to have been constructed in the fifth and sixth century in the southern and southwestern Korean Peninsula, which is considered to have been under the control of Wa (the oldest recorded name for Japan).

Small-scale, keyhole-shaped tumuli or round and square barrows are built next to large-scale, keyhole-shaped tumuli that are commonly found throughout Japan with the Kinki region being the main area. In addition, a kofun-tumuli group composed of large-scale tumuli is formed in many locations. Most of the giant above-ground tombs that were built in the Kofun Period are keyhole-shaped tumuli. Daisenryo-kofun Tumulus (which is said to be the mausoleum of Emperor Nintoku) is the largest of all. Its surface area is bigger than that of the pyramid of the King Khufu or that of the mausoleum of the first Quin Emperor. And, as such, it is the largest above-ground tomb in the world. The total length of the burial mound is 486 meters. Its height is thirty-six meters. This tomb is surrounded by a triple moat.

The End

The style of constructing keyhole-shaped tumuli began to change in the sixth century. Most of those built in the west of the Kanto region were smaller in size. Larger keyhole-shaped tumuli with a burial mound longer than 100 meters were concentrated in the Nara Basin and the Kinai region (five central provinces surrounding the ancient capitals of Nara and Kyoto, namely Yamato, Kawachi, Settsu, Izumi, and Yamashiro that are now the municipalities of Kyoto and Osaka and the prefectures of Nara and Hyogo) including Furuichi-kofun Tumuli Group, with some exceptions such as Iwatoyama-kofun Tumulus in Kyushu and Danpusan-kofun Tumulus in Owari.

The size difference also grew larger, not only between Iwatoyama-kofun Tumulus and Danpusan-kofun Tumulus, but also between the tumuli that most likely belong to Okimi (His Majesty) and the rest inside the Kinai region. This is thought to reflect a change in the social system of the time. The tombs that are considered to be of Okimi, including Kawachi Otsukayama-kofun Tumulus, Mise Maruyama-kofun Tumulus, and Imashirozuka-kofun Tumulus, in particular, dominate the rest in size. It is believed that the power that had previously been shared among dominant chiefs began to concentrate in the hands of Okimi. The sixth-century tombs that are presumed to belong to Okimi, like Mise Maruyama-kofun Tumulus, are built somewhere away from the kofun-tumuli groups that were formed by the continuous construction of Okimi tombs beginning in the third century, such as Furuichi-kofun Tumuli Group, Mozu-kofun Tumuli Group, Umami-kofun Tumuli Group, Sakitatenami-kofun Tumuli Group, and Oyamato and Yanagimoto-kofun Tumuli Group. This also suggests that the power structure involving Okimi (of Yamato Sovereignty) changed in the sixth century.

Additionally, the style of keyhole-shaped tumuli went through some changes. Baicho disappeared. The use of fuki-ishi (stones covering the surface of a burial mound) diminished. The standard number of terraces was reduced from three to two. Furthermore, the use of haniwa (burial mound figurines) came to a halt, except in the Kanto region. In short, not only the scale but also the visual appearance of keyhole-shaped tumuli deteriorated in the sixth century. It would appear that the social significance of keyhole-shaped tumuli of the time was also beginning to change.

In contrast, unlike elsewhere, in the Kanto region, many keyhole-shaped tumuli including those with burial mounds being as long as 100 meters such as Saitama-kofun Tumuli Group were constructed in the sixth century. Keyhole-shaped tumuli were build with regional characteristics, such as Saitama-kofun Tumuli Group with a rectangular double moat and a keyhole-shaped tumulus in Shimotsuke with a wide plane surface called kidan (a platform on which a tomb was placed). During the sixth century, across-the-board regulations concerning the construction of tombs were yet to be implemented nationwide.

From the time when they first appeared, construction of keyhole-shaped tumuli, including large-scale tumuli that are considered to be the mausoleums of Okimi, was concentrated in Kinai
However, the keyhole-shaped tumulus built in the Furuichi-kofun Tumuli Group in the mid-sixth century was the last constructed in any of the kofun-tumuli groups found in Kinai. In the latter part of the sixth century, construction of these tombs ceased throughout the country. The shape of the mausoleums of Okimi also changed from a keyhole to a square after the construction of Mise Maruyama-kofun Tumulus, Umeyama-kofun Tumulus and Taishi Nishiyama-kofun Tumulus, all of which are believed to have been built in the second half of the sixth century. Keyhole-shaped tumuli continued to have been built in some regions such as Kanto and Suo between the beginning and the first half of the seventh century. However, their construction came to an end for the most part by the late sixth century. Afterward, the tombs of the chiefs changed mainly to round and square barrows in shape. Some tombs of the chiefs such as those of Okimi changed to polygon-shape including octagon-shape.

Keyhole-Shaped Tumuli

Keyhole-shaped tumuli consist of various elements including a burial mound (the front square, the rounded rear, and tsukuridashi, or a space for religious ceremonies), burial facilities (a coffin room, a compartment protecting coffin room, and a stone chamber), gravel goods, and external facilities (fuki-ishi for hardening the mound covering a tomb and the earthenware, haniwa, and the other related items used in rituals).

The Rounded Rear

The rounded rear is the most important part of the keyhole-shaped tumuli. This is because it was there where the deceased chief was buried and grand burial rituals were held. Its top is narrow and flat. Its shape is suited for burying the deceased in the ground underneath. The distance from the bottom to the top is made large. On the average, the grade of its inclined plane is twenty-five to twenty-six degrees. However, it can be steeper. Fuki-ishi were laid on the slope at the time of the construction to keep people from climbing. There is a feature designed to permit people to climb on the rounded rear via the front square.

It is called ryuki shado (a rising, slanting road). With installation of ryuki sado, the front square and the rounded rear are connected. However, it is often difficult to reach the top and a burial pit underneath by using ryuki sado alone. Thus, horiwari bodo (a trench path to the tomb) leading up to the pit was built in the middle of the sloping road.

The slopes of the constricted portion and the square front are also made steep. It makes climbing difficult. A funeral procession can climb on either the right or left corner at the front of the square front. These areas were designed to form a gentle slope to facilitate climbing. As described above, it can be said that keyhole-shaped tumuli are surrounded by steep slopes to discourage people from climbing. This means one must refrain from climbing. Keyhole-shaped tumuli are constructed as forbidden areas.

The Front Square

With respect to the oldest keyhole-shaped tumuli, the frontal surface of the square front is shaped like a plectrum, as that in the third-century Hashihaka-kofun Tumulus. The anterior surface width of the front square is comparable to the diameter of the rounded rear. Such tumuli include Tsubai Otsukayama-kofun Tumulus in Yamashiro-cho, Soraku-gun, Kyoto Prefecture. The rounded rear is built higher than the front square. With the subsequent model of keyhold-shaped tumulus, the square front extends straight toward the front. It is also low and narrow. For instance, Chausuyama-kofun Tumulus in Sakurai City is one of them.

Later, in more recent years (in the middle of the Kofun Period), the width of the front square became comparable to the diameter of the rounded rear. In subsequent years, the front square continued to become larger.
The frontal-width of the front square of tumuli is 1.5 times to sometimes twice the diameter of the rounded rear
There are many tumuli (of the late Kofun Period) having the square front that is higher than the rounded rear.
Some keyhole-shaped tumuli of the late Kofun Period have a shape referred to as 'kenbishi-gata'
The center of the square front is somewhat angular and is projecting outward like the Japanese letter 'へ' in this form.
(Kenbishi-gata is found only in Imashirozuka-kofun Tumulus, Kawachi Otsukayama-kofun Tumulus, Mise Maruyama-kofun Tumulus, Toriya Misanzai-kofun Tumulus, and Kawarazuka-kofun Tumulus.)
(As seen from the above, there are very few Kenbishi-gara tumuli.)


No tsukuridashi has been found in the oldest model of keyhole-shaped tumuli. It is found in the constricted portion of the large-scale, keyhole-shaped tumuli whose burial mound is longer than 200 meters. It is installed in the large-scale, keyhole-shaped tumuli of Sakitatenami-kofun Tumuli Group as well as those of Umami-kofun Tumuli Group in the east of the Nara Basin. It is also set up in the large- and middle-scale, keyhole-shaped tumuli of Furuichi-kofun Tumuli Group and Mozu-kofun Tumuli Group. In some cases, burial services were held in tsukuridashi. Not only are haniwa lined up, but also figural haniwa are placed there. The fact that rituals and tsuiso (the burial of an individual in the same tumulus which has already been occupied by the remains of another person) were held in tsukuridashi built near the foot of the constricted portion of the tumulus and not at the summit suggests that there may have been a change in attitude towards funeral rites. It is considered that the top of a tomb being regarded as a forbidden and revered area had something to do with such a change. It is believed that tsuiso and rituals stopped being held after a certain period of time.

Earthenware for Rituals

The earthenware used in burial rituals include the Miyayama-type special vessel stands and jars as well as the Totsuki-type cylindrical haniwa, which is said to be the oldest haniwa evolved from the foregoing along with the next oldest group of haniwa including special jar-shaped haniwa, cylindrical haniwa, house-shaped haniwa, weapon-like haniwa and human-shaped haniwa. Unlike vessel stands and jars for everyday use, special earthenware is large and has decorative patterns. Some vessel stands are as much as one meter in height and jars are approximately forty to fifty centimeters tall. When being placed on a vessel stand, the top of the jar will be as high as one's shoulder. It is considered that rituals were held to succeed to the soul of the deceased chief and the chieftainship, using those big utensils which attract attention.

A Stone Chamber Dug into the Side of a Slope

A stone chamber dug into the side of a slope is a large open space. Not only the remains of one person but also his family members and blood relations can b buried there. It is very different from the previous burial method in which one deceased person (such as the chief) was buried in a stone-lined dugout. Hence, there were changes in burial concepts and facilities.

Burial rituals take place in the following order: ascend to the top of the front square via a corner (on either the right or left of the frontal surface of the square front), descend toward the rounded rear, go up the ryuki shado (a slope built to make it easier to climb to the rounded rear), and enter the burial pit through a horiwari bodo (a path to the stone chamber). The stone chamber is built on the top of the rounded rear with its entrance facing the front square. Examples of the stone chamber built in accordance with ancient ritual as mentioned in the foregoing can be seen in Roji-kofun Tumulus and Sukizaki-kofun Tumulus in Fukuoka Prefecture.

Keyhole-Shaped Tumuli in the Southern Korean Peninsula

Hwangnam Great Tumulus in Kyŏngju, Silla, with its total length measuring 120 meters, is known to be the oldest tumulus in the Republic of Korea. However, it is composed of two round mounds, being a different variety from keyhole-shaped tumuli in Japan.

Yet, keyhole-shaped tumuli were found one after another in the southwestern Korean Peninsula after the introduction of Shokakudo No. 1 Kofun Tumulus, which is located in Kosŏng, South Kyŏngsang, the Republic of Korea, as one of them in 1993. The subsequent investigation revealed that Shokakudo No. 1 Kofun Tumulus consisted of three overlapping round barrows with each of them having been built in different times whereby it became apparent that it was not a keyhole-shaped tumulus. On the other hand, there are eleven and two keyhole-shaped tumuli that have been confirmed to date in South Chŏlla and North Chŏlla, respectively.

All of the keyhole-shaped tumuli in the Korean Peninsula were built in a very limited time period between the latter half of the fifth century and the middle of the sixth century. They are only seen in Gaya near the border of Paekche. The length of these burial mounds varies in the range of 80 to 100 meters. It is known that some Japanese artifacts, such as cylindrical haniwa, items made of seashells from the southern islands and a stone chamber painted with red-ocher inside have been found in these burial mounds. The discovery mentioned in the foregoing generated an opinion suggesting that these keyhole-shaped tumuli may have been tombs of the local lords of Gaya who joined forces with powerful Japanese to retaliate against Paekche, which, in an attempt to advance southward, was putting enormous pressure on Gaya in those days when Gaya also actively adopted culture and customs of Japan. The size of these keyhole-shaped tumuli was fundementally decided by how close those local lords were to the Imperial Court as well as their status. With regard to chiefs of tribes and communities that were subordinate to the Imperial Court, their keyhole-shaped tumuli are often eighty to 100 meters in length. These examples are also found in the Tohoku region of Japan prior to the seventh century.

There is also another opinion that they are the tombs of the Japanese lords who were sent from Japan as provincial governors such as Hozumi no Omi Oshiyama (as mentioned in the chapter covering 512 of "Nihon Shoki" (The Chronicles of Japan)). The individuals buried in these tombs remain unidentified to date.

[Original Japanese]