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 comes from the natural cave formations that have served local communities for generations as storage spaces. Visitors can observe how traditional Japanese engineering practices integrated these geological features with simple structural additions.
Access requires a 15-minute walk from the parking area, with guided tours available during operating hours from April through November. Visitors should bring appropriate footwear since the interior spaces are damp and cool.
The facilities stored more than one million trays of silkworm eggs while keeping temperatures just above freezing, even when external conditions reached 20 degrees Celsius (68 Fahrenheit). This remarkable feat relied entirely on the natural ventilation system built into the cave network.
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