Chausuyama Tomb and Ko-Chausuyama Tomb

Chausuyama Kofun and Kochausuyama Kofun: Ancient Tombs Above Lake Biwa

A grass-covered mound about 122 meters long runs along a low ridge on the southern shore of Lake Biwa, in the Zeze district of Otsu City. This is Chausuyama Kofun, a burial mound raised roughly 1,600 years ago for a powerful local figure. Its outline belongs to the type that defines Japan's Kofun period: a round rear knoll joined to a flaring, trapezoidal front. Seen from above, the form resembles an old-fashioned keyhole, and English writing on Japanese archaeology often calls these structures keyhole tombs.

The national designation actually covers two mounds. The large keyhole tomb shares its protected status with a smaller round mound a couple of hundred meters to the south, known as Kochausuyama, literally "little Chausuyama." Together they were registered as a National Historic Site in 1921. The wooded slope that holds them is now a neighborhood green space, and most residents simply call it Chausuyama Park.

The larger tomb is substantial. Its rear circle measures about 70 meters across and stands roughly 8 meters high, while the front projection runs about 60 meters long and 58 meters wide. The front section points east, toward the lake basin below. To walk its length is to cross the work of a community that moved a great deal of earth without metal tools or wheeled carts.

Who Lies Beneath the Mound

The Kofun period takes its name from these earthen tombs, built across the Japanese archipelago between roughly the third and seventh centuries for rulers and the families around them. Chausuyama Kofun is dated to the closing years of the fourth century or the opening years of the fifth. By that time the southern shore of Lake Biwa had become a corridor of movement and trade, and a chief buried here would have controlled land, labor, and the routes that crossed it.

The identity of the person interred remains unknown. The burial chamber itself has never been located, so the questions an excavation might answer are still open. Local tradition has long supplied two candidates. One is Hikoimasu-no-okimi, a prince of legend tied to the early royal lineage. The other is the household of Prince Otomo, the figure later honored as Emperor Kobun.

That second tradition carries a vivid story. In 672, the succession dispute known as the Jinshin War ended in defeat for the Omi court, and Prince Otomo took his own life at the age of twenty-five. Five low mounds survive on the summit of the rear circle, and local accounts connect them to that episode, calling them the burial mounds. The connection is best understood as folklore rather than fact: the tomb predates the war by some two and a half centuries, so the legend was attached to an already ancient monument long after it was raised.

Why the Site Is Protected

Chausuyama Kofun received its status as a National Historic Site on 3 March 1921, more than a century ago, under the criterion covering shell mounds, settlement remains, tombs, and similar sites. Its scale is part of the reason. At about 122 meters, it ranks third among the keyhole tombs of Shiga Prefecture, after Azuchi Hyotanyama Kofun in Omihachiman, near 134 meters, and Kojinyama Kofun in Hikone, near 124 meters.

Size alone, though, is not what gives the mound its scholarly weight. Its proportions closely match those of Saki Misasagiyama Kofun in Nara, one of the great tombs of the Yamato heartland. Several mounds across central Japan share that same template, and they sit in a rough ring around the Kinai region. Many archaeologists read this distribution as evidence that political authority radiating from Yamato reached the surrounding provinces when these tombs were built. Chausuyama Kofun, in that view, marks the point where a Lake Biwa community was drawn into a wider order, its chief expressing rank through a borrowed and recognizable form.

What to Look For on a Visit

A path climbs the mound from the shrine area, and the route makes the tomb's construction easy to read. The builders shaped the surface in tiers and finished it with a skin of fitted stones, a technique known as fukiishi. Rows of haniwa once stood along each level. Haniwa are unglazed terracotta objects, in this case plain cylinders set in lines, with figurative pieces placed near the summit. Surveys have detected both kinds here. Time has buried most of these features under grass and soil, so the visitor sees a green slope rather than a stone-clad pyramid, but knowing what lies beneath changes how the mound reads.

On the summit of the rear circle stand the five small mounds tied to the Prince Otomo tradition, marked by weathered stone. Lower down, near the waist where the round and rectangular sections meet, sits Akiba Shrine, dedicated to a deity invoked for protection against fire. The shrine is a later addition to the tomb, and its quiet presence is part of how the site has been used and cared for over the centuries.

Kochausuyama, the companion mound to the south, is a round tomb roughly 18 meters in diameter. It has never been excavated, so its date and contents are unconfirmed. Its position close to the larger tomb has led to the suggestion that it is a satellite mound, the resting place of someone connected to the chief buried in Chausuyama Kofun. Standing between the two, you are looking at a small ancient cemetery rather than a single grave.

Planning Your Visit

The tombs sit within Chausuyama Park, an open public space with no admission fee and no fixed gate hours. There is no museum or visitor center on the grounds, and the experience is closer to a walk through a wooded local park than a guided heritage site. Information boards near the mound outline its history for those who want context on the spot.

The nearest station is Zeze-Honmachi on the Keihan Ishiyama-Sakamoto Line, about a fifteen-minute walk away. The route crosses railway tracks before climbing toward the ridge. Comfortable shoes are sensible, since the mound paths are unpaved and uneven in places. Early morning is a pleasant time to come, when the light is soft and the park is used mainly by residents out walking or jogging.

Around the Neighborhood

The Zeze district rewards a longer stay. A short distance toward the water lies Zeze Castle Ruins Park, on the site of a lakeside fortress begun after the Battle of Sekigahara. The castle was a water castle, its defenses built to use the lake itself, and although the keep is long gone, the grounds are a well-loved spot for cherry blossoms in early April. Several of the castle's gates survive, having been moved to nearby shrines and recognized as Important Cultural Properties.

The shoreline of Lake Biwa is close at hand, with paths along the water and views toward the long span of the Omi Ohashi bridge. Combining the ancient mound, the early-modern castle site, and the lake itself makes for a single afternoon that moves across more than a millennium and a half of the region's history.