Arafune-Azumaya Cold Storage Facilities, Historic storage facility in Gunma Prefecture, Japan

The Arafune-Azumaya facility comprises three large cave structures built into mountain slopes that maintain near-freezing temperatures through natural airflow from snow-filled crevices. The caves have been fitted with simple walls and seals to regulate temperature and control moisture levels inside.

In the early 1900s, these cold storage facilities enabled year-round production by preserving silkworm eggs at constant temperatures. This cooling technology proved essential to Japan's silk industry and its global trade expansion.

The name fūketsu refers to wind caves that blow cold air in summer; local people had long used such caves to store pickles before silkworm eggs. The Arafune site's operator, Shunjūkan, took its name from a wish to raise autumn eggs to the quality of spring eggs. The Azumaya cave is also called Agatsuma or Tochikubo fūketsu.

Arafune is about 25 minutes by car from Shimonita Station on the Joshin Dentetsu line, or roughly 30 km from the Shimonita Interchange; the town office advises sturdy clothing, warns that mobile phones barely work in the mountains, and notes bears and snakes along the way. Azumaya has no visitor facilities.

The No. 1 cave has a frontage of 7 m and a depth of 3.5 m, No. 2 measures 11.5 m by 3.5 m, and No. 3 is 8 m by 3.5 m. Cold air still blows from the masonry at about 2 °C year round, though the clay-walled storehouses above were lost in the 1950s.