Guida
Arafune Fuka is a facility located in Shimonita Town, Gunma Prefecture, used for storing silkworm eggs (eggs of the silkworm) during the Meiji and Taisho eras. By utilizing the natural topography, the facility harnessed the cold air blowing from the crevices in the rocks to maintain a constant temperature, controlling the hatching-time of the silkworms. This site is designated as a component of the UNESCO World Heritage site 'Tomioka Silk Mill and Related Sites,' serving as a vital cultural heritage that tells the story of the sericulture industry that supported Japan's modernization. Its massive scale and the ingenious structure that masterfully utilizes natural forces demonstrate the high level of technical skill present during that era.
During the Meiji era, securing a stable supply of silkworm eggs was essential for the production of raw silk, which was one of Japan's primary exports. Controlling the hatching time through temperature regulation was the key to increasing productivity. Arafune Fuka was developed around 1905 (Meiji 38) to 1914 (Taisho 3). Built by the father-son duo Seitaro and Chiju Niwa, the facility created a stable environment regardless of the season by using the natural cold air. At its peak, the silk industry involving this technology was so significant that it facilitated trade across a wide area, including the Korean Peninsula. Today, the stone-stacking structures are preserved as precious historical sites that symbolize the development of modern sericulture.
The most striking feature is the sophisticated stone-built wind cave structure. Originally, a building similar to a storehouse stood above the cave, and the facility used a three-layer structure (two underground levels and one ground level) to regulate temperature. Although the upper building is gone, the remaining stone-stacking ruins allow visitors to appreciate the ingenuity used to manage natural cold air efficiently. The surrounding area also includes related historical sites like the 'Higashidani Fuka,' making the entire region a living museum of the silk industry. Occasional guided tours are available to provide deeper insights into the structure and its historical context.
Because Arafune Fuka naturally emits cold air, it is highly recommended to visit during the warmer months (June to August). You can enjoy a refreshing experience while exploring the historical space. However, as the site is located on a sloping mountain area, please be mindful of temperature changes and the terrain. Visiting during daylight hours is best for observing the details of the stone structures and the natural landscape.
Free guided tours by local staff are often available (though groups must book in advance). Through these tours, you can learn about the specific sericulture techniques used and the reasons why this specific location was chosen. It is also highly recommended to visit the nearby 'Shimonita Town History Museum.' The museum features materials related to Shunkokan (the organization that managed the cave) and the Shimonita War, providing a multi-dimensional understanding of the local history.
The area around Arafune Fuka is a beautiful blend of nature and history. The 'Higashidani Fuka' in Nakajo Town is another significant wind cave that adds to the regional historical value. Additionally, the Shimonita Town History Museum offers a deep dive into the silk industry that drove regional development. Visiting these spots together will give you a more profound understanding of the role the silk industry played in Japan's modernization.