Deep inside a complex of caves carved into a Tochigi Prefecture mountainside lie rows and rows of bottles of sake.

Here, no sunlight penetrates and, with an average temperature of 10 degrees Celsius, the underground shelter is said to provide the perfect conditions to age and bring out bold, new flavors in Japan’s national drink.

This is the cavernous storehouse of Shimazaki Brewery in Nasukarasuyama, a small town tucked away in the countryside north of Tokyo in Tochigi. The brewery itself has been around since 1849, and over the past half-century it has built up a reputation as a pioneer in aged sake.