Urama Chausuyama Tomb

Urama Chausuyama Kofun: The Oldest Grand Keyhole Tomb of Ancient Kibi

Rising quietly from a hilltop in eastern Okayama City, Urama Chausuyama Kofun stands as one of the most historically significant burial mounds in all of Japan. Built at the end of the 3rd century during the earliest phase of the Kofun period, this imposing keyhole-shaped tomb (known as a zenpō-kōen-fun in Japanese) is the oldest large-scale burial mound in the ancient Kibi region — a kingdom that once rivaled the mighty Yamato court in power and influence.

Designated as a National Historic Site in 1974 and recognized as a component of the Japan Heritage story "The Birthplace of the Momotaro Legend — Okayama" in 2024, Urama Chausuyama Kofun offers visitors a rare window into the dawn of Japan's ancient state formation. Its distinctive shape, impressive scale, and the mysteries surrounding its occupant continue to fascinate archaeologists and history enthusiasts from around the world.

A Half-Scale Replica of the Legendary Hashihaka Kofun

What makes Urama Chausuyama Kofun truly remarkable is its precise relationship to the Hashihaka Kofun in Sakurai, Nara Prefecture — a tomb widely considered to be the burial place of Queen Himiko of Yamatai-koku, the legendary queen mentioned in ancient Chinese historical texts. Research by Professor Yoshitaka Hōjō of Tokai University has demonstrated that Urama Chausuyama Kofun is an exact half-scale replica of the Hashihaka Kofun, sharing the same proportions and design features.

This discovery carries profound implications. Among all the proportionate-scale replicas of Hashihaka Kofun found across Japan, Urama Chausuyama Kofun is the largest outside the Kinai region (the Kyoto-Osaka-Nara heartland of ancient Japan). This strongly suggests that the person buried here was a ruler of great importance — someone who played a key role alongside the Yamato court in the formation of the earliest Japanese state.

Tomb Dimensions and the Oldest Keyhole Design

Urama Chausuyama Kofun measures approximately 138 meters in total length, with a rear circular mound (kōen-bu) about 81 meters in diameter and roughly 13.8 meters in height, while the front rectangular section (zenpō-bu) extends approximately 61 meters. The front section widens in a distinctive "plectrum shape" (bachi-gata), resembling the pick used to play a shamisen — a hallmark feature of the very earliest keyhole-shaped tombs in Japan.

The rear circular mound was constructed in three tiers and originally covered with stone paving (fukiishi). The top of the front section sits approximately 4 meters lower than the summit of the rear mound. This particular combination of features represents the oldest form of keyhole-shaped burial mound, linking Urama Chausuyama Kofun directly to the very origins of kofun culture in Japan.

Why It Was Designated a National Historic Site

Urama Chausuyama Kofun was designated a National Historic Site in 1974 (Showa 49), a decision driven by the urgent need for preservation. In 1969, the site faced the threat of destruction due to residential development in the surrounding area. The designation recognized the tomb as a representative example of an early Kofun period burial mound in the San'yōdō corridor of the Kibi region.

The tomb holds immense archaeological and historical value for several reasons: it represents the earliest form of keyhole-shaped tomb construction; it demonstrates the powerful alliance between the Kibi kingdom and the Yamato court at the dawn of the Kofun period; and its surviving artifacts provide crucial evidence about ritual practices, burial customs, and inter-regional exchange networks in 3rd-century Japan. The tomb was additionally recognized as a component cultural property of the Japan Heritage "Momotaro Legend" story in 2024, further cementing its cultural significance.

Archaeological Discoveries: The 1988 Excavation

In 1988, a major archaeological excavation led by Professor Yoshirō Kondō of Okayama University investigated the rear circular mound. At a depth of 2.5 meters below the disturbed upper layers, the team discovered a vertical pit-style stone chamber (tateana-shiki sekishitsu) measuring approximately 7 meters in length and 1.2 meters in width. The chamber was constructed using stacked slabs of andesite, a type of stone believed to have been quarried in northern Kagawa Prefecture or from islands in the Bisan Seto strait — evidence of remarkable long-distance transportation capabilities.

Although the tomb had been looted during the Meiji era (around 1900), significant artifacts survived. These included fragments of a fine-line animal-band mirror (saisen-shiki jūtai-kyō), 19 bronze arrowheads, 42 iron arrowheads, iron swords and daggers, agricultural tools such as sickles and plow tips, woodworking tools including chisels and axes, and fishing implements like harpoons. The chamber floor was lined with clay containing red pigment (likely vermilion), and a split-bamboo wooden coffin (waritake-gata mokkan) had originally been placed inside.

Among the most important finds were fragments of special vessel-stand haniwa (tokushu-kidai-gata haniwa) and special jar-shaped haniwa (tokushu-tsubo-gata haniwa) — the oldest forms of haniwa known in Japan. These distinctive ceremonial vessels, closely associated with the Kibi region, have also been found at the Hashihaka Kofun and other earliest keyhole tombs, further strengthening the link between ancient Kibi and the formation of the Yamato state.

The Mysteries of Ancient Kibi

One of the most intriguing aspects of Urama Chausuyama Kofun is the mystery surrounding its occupant. Despite being the oldest and largest early Kofun period tomb in the Kibi region, there are no prominent settlements, preceding burial sites, or successor tombs in the immediate vicinity. This is highly unusual — most powerful rulers of the Kofun period can be placed within a clear lineage of tomb construction in a specific area.

Who was the king buried here? What was this ruler's relationship with the dominant power center along the Ashimori River, which had been the heart of Kibi's strength before this tomb was built? These unresolved questions give Urama Chausuyama Kofun an air of mystery that continues to drive archaeological research and historical debate.

The Kibi kingdom itself occupies a fascinating place in Japanese history. Ancient texts record that Kibi was one of the most powerful regional polities in early Japan, with marriage alliances connecting Kibi elites to the imperial line. Some scholars believe that the Yamato and Kibi rulers may have shared a form of dual governance over early Japan, until the Yamato court eventually brought Kibi under centralized control — an event that may be reflected in the famous Momotaro (Peach Boy) legend of Okayama.

Connection to the Momotaro Legend: A Japan Heritage Story

In 2024, Urama Chausuyama Kofun was added as a component cultural property of the Japan Heritage story "The Birthplace of the Momotaro Legend — Okayama." This story connects the ancient archaeological heritage of the Kibi region to the beloved Japanese folktale of Momotaro, the boy born from a peach who defeated demons with the help of a dog, a monkey, and a pheasant.

Scholars believe the Momotaro tale has its roots in the legend of Kibitsuhiko-no-Mikoto, a prince dispatched by the Yamato court to subdue Ura (also called Onra), a fearsome figure who ruled from the mountaintop fortress of Kinojō. The giant kofun tombs of the Kibi region, including Urama Chausuyama Kofun, serve as physical evidence of the powerful kingdom that inspired these timeless stories. Visiting this tomb allows travelers to step into the historical landscape that gave birth to one of Japan's most cherished legends.

Highlights and What to See

Today, the front rectangular section of the tomb has been transformed into a small park with cherry trees, creating a beautiful scene during spring (late March to early April). The rear circular mound is covered with bamboo groves, and the summit still bears the large depression left by the Meiji-era looting. Visitors can walk around the base of the tomb and climb to the top to appreciate its impressive scale.

The site changes character with the seasons: cherry blossoms in spring, lush greenery in summer, autumn foliage, and quiet winter landscapes all offer different atmospheres for exploration. A preservation society (Urama Chausuyama Kofun Hozonkai), established in November 2023, actively maintains the site and organizes educational events.

For those interested in seeing artifacts excavated from the tomb, the Okayama City Archaeological Center (Okayama-shi Maizō Bunkazai Center) houses exhibition materials including examples of the distinctive Totsuki-type cylindrical haniwa found at the site. The center provides excellent context for understanding the tomb within the broader archaeology of the Kibi region.

Nearby Attractions

Urama Chausuyama Kofun is ideally situated as a starting point for exploring the rich archaeological heritage of the Kibi region. Nearby sites and attractions include:

• Tsukuriyama Kofun (Okayama City) — At approximately 350 meters in length, this is the largest kofun in the Kibi region and the fourth-largest in Japan. Built in the early 5th century, it is one of the few giant kofun that visitors can climb and explore freely.
• Kibitsu Shrine (Okayama City) — A grand shrine dedicated to Kibitsuhiko-no-Mikoto, the legendary hero of the Momotaro tale. Its main hall and worship hall are designated National Treasures, and the shrine's Narukama ritual (cauldron divination) is a fascinating experience.
• Kibitsuhiko Shrine (Okayama City) — Another shrine honoring the same deity, set at the foot of Mount Nakayama with beautiful grounds and historical significance.
• Kinojō (Oni-no-Shiro) (Sōja City) — An ancient mountain fortress with panoramic views, traditionally believed to be the stronghold of the demon Ura in the Momotaro legend.
• Ryōgūzan Kofun (Akaiwa City) — A 206-meter keyhole tomb featuring a rare double moat, representing Kibi's power in the late 5th century.
• Okayama Castle and Korakuen Garden — One of Japan's top three landscape gardens, located in central Okayama City, offering a perfect complement to archaeological sightseeing.