Iwajuku Museum in Midori City, Gunma Prefecture, is a unique museum dedicated to the Paleolithic Period of Japan, also referred to here as the “Iwajuku Period.” Centered on archaeological discoveries from the Iwajuku Ruins, the museum introduces the lives of prehistoric people and the natural environment of the Japanese Archipelago from approximately 40,000 to 15,000 years ago.
In addition to stone tools excavated from Iwajuku, the museum displays archaeological materials related to Paleolithic cultures from other parts of Japan. These exhibits provide a broader understanding of prehistoric life, technology, and cultural development.
One of the most impressive exhibits is a full-size replica of a mammoth skeleton, symbolizing the Ice Age environment. Its imposing appearance has also made it the inspiration for Midomo, the mascot character of Midori City.
Around 1946, amateur archaeologist Chūyō Aizawa discovered chipped stone tools in the Kanto Loam Layer, a distinctive reddish soil layer found across the Kanto region.
At the time, this loam layer was generally regarded as natural ground, and it was widely believed that there were no traces of human activity beneath it. In 1949, however, an excavation conducted by Meiji University uncovered stone tools within the loam layer, demonstrating that a Paleolithic culture had existed in Japan before the Jōmon Period.
This discovery became a major turning point in Japanese archaeology. At Iwajuku Museum, visitors can learn about the circumstances surrounding the discovery, the excavations that followed, and the significance of an archaeological finding that challenged the prevailing understanding of Japan’s earliest history.
The permanent exhibition features a wide range of artifacts, including the spearhead-shaped point discovered by Chūyō Aizawa, materials from the Iwajuku I and II stone tool cultures, and artifacts from excavation areas such as Site D, the Parking Lot Site, and the Iwajuku II Site.
Stone tools were discovered in different layers of the Kanto Loam Layer, revealing two distinct cultural stages dating to approximately 30,000 years ago for the Iwajuku I Culture and approximately 20,000 years ago for the Iwajuku II Culture.
Stone materials included shale, obsidian, agate, and andesite. A variety of tools were produced, including knife-shaped tools, scrapers, and cores.
The exhibits also explain the materials used to make stone tools and the manufacturing process, showing how prehistoric people struck and shaped stones to create sharp cutting edges.
The Iwajuku Period corresponded to the Ice Age, when the climate was considerably colder than it is today. Volcanic activity was also active, and volcanic ash layers such as Aira-Tn (AT) volcanic ash have been identified within the geological record.
Models and illustrated displays recreate the landscape and natural environment of this period, helping visitors visualize what the Japanese Archipelago may have looked like during the Ice Age.
A particularly valuable exhibit is the skull of a giant deer, which provides evidence of the large animals that once inhabited the region.
Together with the mammoth skeleton replica, the exhibit helps visitors appreciate the scale and diversity of the natural environment in prehistoric Japan.
The museum also focuses on the daily lives of prehistoric people, whose subsistence depended largely on hunting and gathering.
Exhibits explain how different stone tools may have been used, differences between regional cultures, and the spread of microlithic cultures across prehistoric Japan.
A diorama based on a pit-trap feature discovered at the Hatsunegahara Site in Shizuoka Prefecture provides an illustration of how people of the Iwajuku Period may have hunted animals.
The exact details of prehistoric hunting practices are not completely known, but the display provides an engaging way to consider how people may have adapted to their environment and obtained food during the Ice Age.
At Site B of the Iwajuku Ruins, the Iwajuku Dome, officially known as the Historic Site Iwajuku Ruins Archaeological Remains Preservation and Observation Facility, allows visitors to observe a cross-section of the Kanto Loam Layer at close range.
Seeing the layers of earth with your own eyes provides a tangible sense of how geological time and human history have accumulated over thousands of years.
The Iwajuku Ruins were designated a National Historic Site in 1979, with additional areas subsequently receiving designation. Preservation and archaeological research have continued ever since.
Today, approximately 10,000 Paleolithic archaeological sites have been identified throughout Japan, and Iwajuku remains an important starting point for research into this earliest period of Japanese prehistory.
Iwajuku Museum also holds special exhibitions throughout the year. Topics range from academic and archaeological themes to hands-on exhibitions designed for children.
The museum also offers lectures, educational workshops, and related events, making it suitable for families as well as school field trips.
Iwajuku Museum is more than a place where ancient stone tools are displayed. It tells the story of an archaeological discovery that transformed understanding of Japan’s earliest history, while offering visitors an opportunity to explore the ingenuity and adaptability of prehistoric people.
When visiting Midori City, consider combining a visit to Iwajuku Museum with the nearby Iwajuku Ruins. Together, they provide an opportunity to explore one of the most important chapters in the archaeological history of Japan.
Standing among the evidence left by people who lived here tens of thousands of years ago offers a fascinating glimpse into the distant past of the Japanese Archipelago.