Iwato Ruins

Iwato Site: A Window into Japan's Ice Age World

Tucked away on a quiet river terrace in Oita Prefecture's interior, the Iwato Site (Iwato Iseki) holds one of the most remarkable stories in Japanese archaeology. Here, more than 20,000 years ago, hunter-gatherers of the Late Paleolithic period made their home above the confluence of the Ono River and its tributary, the Okudake River. From this windswept plateau, archaeologists have recovered stone tools, possible burial remains, and a tiny kokeshi-shaped stone figurine that may be the oldest human-form artifact ever found in Japan. Designated a National Historic Site in 1981, Iwato offers visitors the rare chance to stand where Ice Age people once lived, looked out over the great river valley, and shaped the earliest threads of Japanese spiritual culture.

A Site Carved by Rivers and Volcanoes

The Iwato Site sits on a terrace approximately 32 meters above the present-day riverbed, in the Usuo district of Kiyokawa-machi, Bungo-ono City. The surrounding landscape was sculpted by powerful geological forces — most notably the colossal eruption of Mount Aso roughly 90,000 years ago, whose pyroclastic flows formed the welded tuff cliffs that define this region today. The very name "Iwato," meaning "stone door," refers to the dramatic 50-meter-high, 500-meter-long cliff wall that rises nearby, giving the area an almost otherworldly atmosphere.

For the people who lived here in the Late Paleolithic, this elevated plateau offered everything needed for survival: a commanding view of game trails along the river, access to fresh water below, and abundant stone for toolmaking. The site lies within the Oita Bungoono UNESCO-recognized Japanese Geopark, which interprets the entire region as a living museum of volcanic geology, river erosion, and human adaptation.

Discovery and the Three Cultural Layers

Although local residents had collected stone tools from the Iwato area for decades, formal scientific excavation began in 1967 (Showa 42), when a team led by Professor Chosuke Serizawa of Tohoku University arrived to investigate. Serizawa was one of the pioneers who had proven the existence of Japan's Paleolithic period at the Iwajuku Site in 1949, and his work at Iwato would further reshape understanding of Japan's earliest inhabitants.

The excavation revealed three distinct cultural layers stratified within more than a dozen beds of volcanic ash — a remarkable geological archive. The first cultural layer was identified as lying above the Aira-Tn tephra, a widespread volcanic ash from a massive eruption in Kagoshima, dating its occupation to approximately 22,000 to 24,000 years ago. Within these layers, archaeologists recovered knife-shaped stone tools, scrapers, points, and stone cores in great numbers, demonstrating that Iwato was a long-used workshop and dwelling site.

The Kokeshi-Shaped Stone Figurine

Among the thousands of artifacts unearthed, one small object stands out as truly extraordinary. Discovered in the first cultural layer, the kokeshi-shaped stone figurine (kokeshi-gata sekigu) is a small, slender carving made of green chlorite schist — distinctive because almost all the other stone tools at the site were made from slate. The figurine's simple, elongated form vaguely resembles a traditional Japanese kokeshi doll, which is how it earned its modern nickname.

What makes this object so significant is its age and meaning. Believed to be roughly 20,000 to 24,000 years old, it is widely regarded as the oldest human-form artifact ever discovered in Japan. Its purpose remains a mystery, but scholars suggest it may have served as a ritual object, an amulet, or a charm connected to prayer or magic. If so, it offers a rare and precious glimpse into the spiritual world of Japan's Ice Age people — proof that abstract thought and symbolic expression flourished here tens of thousands of years before the Jomon period.

Could This Be Japan's Oldest Burial?

The story of Iwato deepened in 1979, when a second excavation uncovered what appeared to be a stone-piled tomb (shusekibo). Inside, archaeologists recovered four small fragments of human teeth — identified as parts of an upper right canine and incisor — along with pieces of marine shells, themselves a striking find at an inland mountain site. Because the fragments are so small, researchers have been careful not to declare with certainty that this is a burial. Yet if it is confirmed, the Iwato tomb would be the oldest known burial in the Japanese archipelago, pushing back the documented history of mortuary practice by thousands of years.

Either way, the find raises evocative questions about the lives and beliefs of the people who lived here. Where did the marine shells come from, and what did they mean? Did the Iwato people travel to the distant sea, or trade with coastal communities? These questions remain open, inviting reflection rather than easy answers.

Why Iwato Was Designated a National Historic Site

The Agency for Cultural Affairs designated Iwato as a National Historic Site on March 31, 1981, under the criterion covering shell mounds, settlements, tombs, and similar archaeological remains. The recognition reflects several layers of importance. First, Iwato is one of the most representative Late Paleolithic sites in all of Kyushu, with a clearly stratified sequence that allows scholars to trace cultural change across thousands of years. Second, the kokeshi-shaped stone figurine is, by current understanding, unique in Japan — no comparable object of similar age has been found elsewhere. Third, the possible burial feature offers an unparalleled window onto the social and spiritual lives of early modern humans in the archipelago.

Subsequent investigations by Beppu University and the former Kiyokawa Village Board of Education have continued to expand our understanding of the site, confirming its status as a touchstone of Japanese Paleolithic archaeology.

Visiting the Site Today

Iwato itself is a designated archaeological site rather than a developed tourist facility, so visitors should approach it with the understanding that much of the site lies preserved within fields and farmland. The actual excavated finds — including the famous kokeshi-shaped figurine — are not kept on site. To see related artifacts and learn more about the Late Paleolithic context, the Bungo-ono City Museum (Bungo-ono Shiritsu Rekishi Minzoku Shiryokan) and regional cultural resources offer valuable interpretation.

Reaching the site by car is the most practical option. From JR Bungo-Kiyokawa Station on the JR Hohi Main Line, the area is a short drive away. The surrounding countryside is beautiful in every season, with rice paddies, river views, and the distinctive cliffs that gave the locality its name. Visitors are kindly asked to respect the agricultural use of the surrounding land and to confirm access details with the Bungo-ono City Board of Education or the local tourism association before visiting.

Beyond the Site: Exploring Bungo-ono

Iwato sits within one of Kyushu's most rewarding cultural landscapes. Just a short drive away is Harajiri Falls (Harajiri-no-taki), often called the "Niagara of the East," a magnificent 120-meter-wide, 20-meter-high cascade formed by the same Mount Aso pyroclastic flows that shaped the Iwato landscape. The adjacent Michi-no-Eki Harajiri-no-taki roadside station offers local produce, restaurants, and seasonal tulip and rapeseed flower festivals.

The dramatic Iwato cliffs themselves, where a railway tunnel emerges directly onto a bridge spanning the river, have become a favorite of train photographers. Further afield, the region is dotted with magnificent stone Buddhas — including Sugao Sekibutsu, Ogata Miyasako Sekibutsu, and Inukai Sekibutsu — many carved into the same volcanic tuff that defines this geopark. A visit to Iwato can easily be combined with these attractions to form a deeply layered journey through volcanic geology, ancient prehistory, and medieval Buddhist art.