Danjozan Kofun: The Largest Keyhole Tomb of Western Harima

Rising quietly from a residential neighborhood in eastern Himeji, Danjozan Kofun (壇場山古墳) is a monumental keyhole-shaped burial mound that stands as the largest ancient tomb in the western Harima region. Built during the early 5th century — the Middle Kofun period — this 143-meter-long tomb complex offers visitors a rare and intimate encounter with the powerful chieftains who once ruled the ancient province of Harima (present-day southwestern Hyogo Prefecture). Unlike many of Japan's famous kofun, which can only be viewed from afar, Danjozan Kofun allows you to walk up to the mound and even climb to the summit of the rear circular section, where a 1,600-year-old stone sarcophagus remains partially visible on the surface.

What Is Danjozan Kofun?

Danjozan Kofun is a zenpō-kōen-fun (前方後円墳), or keyhole-shaped burial mound, located in the Mikuninochō-Kokubunji neighborhood of Himeji City, Hyogo Prefecture. When viewed from above, the tomb has the distinctive keyhole outline that characterizes the most prestigious burial mounds of ancient Japan: a large circular mound at the rear (the kōen-bu) connected to a trapezoidal mound at the front (the zenpō-bu). The tomb's total length is approximately 143 meters, making it the third largest kofun in all of Hyogo Prefecture, after the Goshikizuka Kofun in Kobe (194 meters) and the Kumobe Kurumazuka Kofun in Tamba-Sasayama (158 meters).

The main mound is constructed in three tiers (sandan chikusei) and was originally surrounded by a moat approximately 20 meters wide, traces of which are now visible as rice paddies. On the western side of the constricted middle section (kubiré-bu), a tsukuridashi projection has been identified — a feature associated with ritual ceremonies. The surface of the mound was once covered with fukiishi (paving stones), and various haniwa clay figures have been found on the site, including cylindrical haniwa as well as shaped haniwa in the form of houses, shields, and short armor (tankō).

The Sarcophagus of Tatsuyama Stone

One of the most remarkable features of Danjozan Kofun is the stone sarcophagus that remains partially exposed at the summit of the rear circular mound. This is a nagamochi-gata sekkan (長持形石棺), or chest-shaped sarcophagus, characterized by its rope-hanging protrusions (nawakake tokkí) on the lid. The sarcophagus was carved from Tatsuyama-ishi (竜山石), a distinctive rhyolitic hyaloclastite stone quarried in Takasago City, approximately 8 kilometers to the southeast.

Tatsuyama stone was the preferred material for the sarcophagi of great rulers throughout the Kofun period, earning it the epithet "Stone of the Great Kings" (Daiō no Ishi). The fact that not only the main tomb but also its satellite tombs feature Tatsuyama stone sarcophagi is exceptional and suggests that the chieftain buried at Danjozan may have controlled the quarry itself, allowing the stone to be used more freely than at other sites across the Kinai region.

The Satellite Tombs: First, Second, and Third Kofun

Danjozan Kofun was originally surrounded by approximately ten smaller satellite tombs (baichō), though most have been lost to modern development. Three surviving satellite tombs are included in the national historic site designation:

Why Was It Designated a National Historic Site?

The Danjozan Kofun complex was designated a National Historic Site on March 3, 1921 (Taishō 10), making it one of the earlier archaeological sites in Japan to receive official protection. The designation recognizes several aspects of its historical importance:

• It is the largest kofun in western Harima and the third largest in Hyogo Prefecture, reflecting the power and influence of the local ruling elite during the 5th century.
• Its proportions closely mirror those of the Nakatsuyama Kofun in Fujiidera, Osaka — a tomb associated with the imperial court — at roughly half scale. This resemblance points to strong connections between the Harima chieftain and the central Yamato government.
• The use of Tatsuyama stone nagamochi-gata sarcophagi across both the main tomb and its satellite tombs is an exceptionally rare pattern, suggesting local control of an important stone resource that supplied elite burials throughout the Kinai region.
• The presence of diverse haniwa types (cylindrical, house-shaped, shield-shaped, armor-shaped) attests to elaborate funerary rituals befitting a high-ranking ruler.

The Legend of Empress Jingū

The name "Danjozan" (壇場山, literally "Platform Ceremony Mountain") is linked to a legend involving Empress Jingū (Jingū Kōgō), a semi-legendary figure said to have led a military expedition to the Korean Peninsula in the late 4th century. According to local tradition, the Empress stopped at this location during her westward journey and erected a ceremonial platform (dan) to pray for victory. While modern historians regard this legend as a later attribution rather than historical fact, it speaks to the longstanding reverence that local communities have held for this imposing mound.

Visiting Danjozan Kofun: What to See

Unlike many major kofun in Japan that are off-limits to visitors, Danjozan Kofun can be explored on foot. Stairs on the northeastern side of the rear circular mound lead to the summit, where you can see the exposed lid of the Tatsuyama stone sarcophagus with its distinctive rope-hanging protrusions. The experience of standing atop a 1,600-year-old burial mound — with the stone coffin of an ancient ruler beneath your feet — is both moving and thought-provoking.

From the top, you can survey the surrounding landscape, including the rice paddies that trace the outline of the ancient moat. The front section of the mound (zenpō-bu) houses a small Tenman Shrine, adding a layer of living spiritual tradition to the archaeological site. The nearby Yamanokoshi Kofun (Third Kofun) is also worth visiting for its exposed sarcophagus and impressive scale as a square tomb.

Nearby Attractions

The area around Danjozan Kofun was the administrative and spiritual heartland of ancient Harima Province, and several related historic sites can be visited in combination:

• Harima Kokubunji Temple Ruins (播磨国分寺跡) — Just a short walk from the kofun, this nationally designated historic site preserves the foundations of a provincial temple built in 741 by order of Emperor Shōmu. The temple grounds once spanned 218 meters on each side, and foundation stones for the pagoda are still visible.
• Harima Kokubuniji Temple Ruins (播磨国分尼寺跡) — The companion nunnery to the Kokubunji, located nearby in the residential area north of the kofun. A small monument marks the site.
• Himeji City Archaeological Center (姫路市埋蔵文化財センター) — Located within walking distance, this center houses artifacts from local excavations and provides valuable context for understanding the region's rich archaeological heritage.
• Himeji Castle (姫路城) — Japan's most celebrated castle and a UNESCO World Heritage Site, located approximately 15 minutes by train from Gochaku Station. A visit to Danjozan Kofun pairs beautifully with a day exploring Himeji's many cultural treasures.