Arafune Cold Storage

Arafune Cold Storage (荒船風穴, Arafune Fūketsu), located in the forested mountains of Gunma, is a fascinating natural cave that played a pivotal role in Japan’s silk industry. In the early 1900s, silk producers used the cave to store millions of silkworm eggs. The cave’s naturally cool air, drawn from underground rock crevices filled with winter snow, helped preserve the eggs and prevent premature hatching. This enabled silk production to continue year-round, even during the hot summer months. Remarkably, the cave’s temperature stays just above freezing, even on the hottest days.

Designated a UNESCO World Heritage site in 2014, alongside the Tomioka Silk Mill, Arafune Cold Storage offers visitors a rare insight into the history of Japan’s silk production. The site features the foundations of old storage buildings, where the eggs were once kept, and visitors can learn about the cave’s historical significance through brief on-site tours (Japanese only). To reach the cave, visitors can enjoy a 10–15 minute walk downhill through the forest, with a free shuttle bus available on weekends. Taxis are also an option, with drop-off points closer to the site for those who prefer a faster route.