Nakata Cave

A Hole Opened by a Road Crew in 1969

In January 1969, workers widening the Onahama–Yotsukura prefectural road in eastern Fukushima cut into a low hillside and broke open a cavity that had been sealed for roughly fourteen centuries. Behind the soil lay a stone burial chamber, and on its walls were rows of painted triangles in red and white, still legible after all that time. The site is now known as Nakada Yokoana, and it is counted among the finest decorated tomb caves in Japan.

A yokoana is a tomb cut horizontally into a slope rather than raised as a mound. From the late sixth century onward, communities across Japan increasingly buried their dead this way, carving family-scale chambers into soft hillsides instead of building the great earthen kofun of earlier generations. Most yokoana are plain. Nakada is not.

The site sits on the north-facing slope of a sandy tuff ridge, about five kilometers south of the mouth of the Natsui River and roughly 1.2 kilometers inland from the present Pacific shoreline. Five tomb caves were cut into the soft rock here, set in three stepped tiers up the hillside. The lowest of them, Tomb Cave No. 1, is the painted one.

The Warrior in Tomb Cave No. 1

The excavation that followed the discovery recovered an unusually large assemblage of grave goods, around 1,300 items in all. They describe a person of real standing. Among them were fragments of keiko lamellar armor, a gilt-bronze helmet, a gilt-bronze sword, a silver-mounted spearhead, and horse trappings finished in gilt bronze, including one of the largest gilt-bronze horse bells ever found in this country.

Objects of this kind were not made locally on a whim. Gilt-bronze weapons and ornate horse gear were among the items the Yamato court distributed to provincial leaders it wished to bind to itself. Their presence at Nakada points to a local figure with strong political ties to the central polity, buried with the regalia of that connection.

The goods were not found neatly laid out. After the burial, they appear to have been deliberately broken and shifted out of the rear chamber, set instead in the front chamber, around the entrance, and especially in the forecourt outside. Archaeologists read this as the trace of a graveside rite carried out some time after the funeral itself, when the chamber was reopened and the offerings rearranged.

Why the Site Is Protected

Nakada Yokoana was designated a National Historic Site on 11 May 1970. The case for protection rests on several points that rarely coincide at one site.

Decorated tomb caves with two chambers are scarce. The painting program here is comparatively complete, surviving across three walls. The structure is well preserved as well: a drainage channel runs along the passage, and each entrance retains the fittings once used to seal it. And there is the floor, painted red from wall to wall, a feature found at almost no other decorated tomb in Japan.

The artifacts carried their own weight in scholarship. Studied together, they forced a substantial revision of how the late Kofun period and the social role of tomb caves were understood. The grave goods themselves hold a separate designation as a Fukushima Prefectural Important Cultural Property.

Reading the Painted Chamber

Tomb Cave No. 1 measures 6.67 meters from its entrance to the rear wall, divided into a front chamber and a rear chamber. The painting is concentrated in the rear chamber, the space where the body was laid.

Three of its walls carry a continuous triangle pattern in red and white. Each triangle is about 40 centimeters to a side, and the pattern is set out in three horizontal tiers. The top tier points downward; the two tiers below it point up. Look closely and the painter's method becomes visible. Many triangles are outlined with a fine incised line, and some of the red triangles were laid over a white ground rather than applied straight onto the stone.

The wall above the inner entrance breaks the rhythm. There the design abandons the two colors and is worked in red alone: a band of sawtooth set between two curved lines.

Then there is the floor. Red pigment covers its entire surface. Specialists single this out because it appears almost nowhere else, and standing in the chamber it changes the whole sense of the space, as though the burial were set within a single field of color.

The paint is mineral pigment on bare stone. It has lasted because the chamber stayed sealed, dark, and stable in temperature. That same fragility is the reason visitors are kept at a careful distance from it.

Visiting, and Where to See the Treasures

The interior of the tomb cave is not open day to day. To protect the wall paintings, the rear chamber's temperature and humidity are monitored, and the public is admitted only on a small number of scheduled days each year. For a long time this meant a single opening each autumn, though the date can shift; in 2026 it was held in May to coincide with a regional tourism campaign. On those days admission is free and no reservation is required. Anyone hoping to see the chamber should check announcements from the Iwaki City Board of Education or the city tourism office before traveling.

The grave goods are far easier to reach. They are on permanent display at the Iwaki City Archaeological Museum, a short drive away, where the great gilt-bronze horse bell, the armor fragments, and the personal ornaments can be examined up close on any day the museum is open. For most visitors, the museum is the practical way to encounter what Nakada Yokoana actually held.

Iwaki is a sprawling coastal city with the port of Onahama, the Aquamarine Fukushima aquarium, and hot-spring districts inland, so the tomb pairs naturally with a wider day along the coast. By car it is roughly 30 minutes from JR Iwaki Station, and a similar distance from the Iwaki-chuo interchange on the Joban Expressway.