The facility was made between 1905 and 1941 and is located approx. 16 kilometers away from downtown Shimonita at the foot of Mt. Arafune which borders between Gunma and Nagano Prefectures. The inside of the cold storage remains around 2 degrees Celsius even in the middle of the summer.
Sericulture in Japan used to be limited to once a year in spring (May-June), and rearing of multivoltine silkworms was at one time prohibited by the Meiji government because of the quality of its cocoons deteriorated in summer and autumn and rearing was difficult. When Senju Niwaya, a silkworm-raising farmer in Shimonita Town on the south-western edge of Gunma, who studied at the Takayama-sha Sericulture School in 1904, discovered that the cold wind there could be utilized for storing silkworm eggs, his father Seitaro decided to build a silkworm egg storage facility.
In the late 19th century, research on the stable rearing of silkworms in summer and fall progressed, and efforts were made to store silkworm eggs in natural cold storage facilities called fuketsu, that use naturally cold air, in order to adjust the hatching timing. Still, it was difficult to maintain a constant temperature inside the storage facility, so the rate of successful hatching of stored silkworm eggs varied. In late 19th century, knowledge of sericulture, geology, and meteorology was utilized to look for solutions in the selection of a location for the storage system, an ideal structure for the storehouse, and construction of a cold storage system with a scientific temperature control system.
With the support of various parties, both inside and outside of Gunma, the Nos. 1, 2, and 3 cold storages were successively built between 1904 and 1914. Elsewhere in Japan, cold storage facilities used the cold conditions of natural caves, but the Arafune Cold Storage was built on the mountain slopes where cold air flowed, using stone wall foundations. Above this structure was a cellar shed with plastered earthen walls. The buildings consisted of two stories below and one above ground. The three cold storages facilities altogether were capable of storing 1.1 million sheets of paper at one time onto which silkworm eggs were tightly laid, enabling the stable sericulture production in the summer and autumn and therefore meeting the demand for the increased production of cocoons as raw silk exports flourished.
So, this is it. The Arafune Cold Storage! Being located at a height of 840 meters above sea level, it is 2 degrees Celsius even in mid-summer. It stored silkworm eggs from all over Japan and was the largest in Japan. Speaking of largest, as no records have been found on storing silkworm eggs in cold storage or caves in China or in Europe, except for the ones in Italian-French Alps which did not spread widely, Arafune Cold Storage was the largest silkworm egg storage at the time in the world.
From around 1935, due to the spread of electric refrigerators, a natural cold storage was no longer necessary for storing the silkworm eggs, but the local residents continued to use the facilities for storing food. All upper structures were removed by 1955. Shimonita Town made the land a public domain, and the three sets of foundation stone walls are all that is left (see the photo), but the cold air flow mechanism, the connecting passage ways, and the structure devised to seal the seams of the stone walls still remain today in good condition. However, visitors are not allowed inside the cold storage for security reasons.
Sightseeing spots in the vicinity
Tomioka Silk Mill and Related Sites