NASU-KARASUYAMA, Tochigi Prefecture--When one enters a cave dug toward the end of World War II, body sweat produced from the summer heat and humidity instantly dries.

The dark cave, which serves as a natural refrigerator, makes a perfect storehouse for local brewery Shimazaki Shuzo.

“The taste becomes mild when sake is stored here,” said Yusuke Tsuchihashi, 41, a manager of the brewery. “The cave has the best temperature environment for aging sake.”

Toward the end of World War II, the cave was dug on a mountainside to produce tank components. When it was completed, the war had ended, and the cave ended up unused.

“I heard that tanks were built at the skirts of the mountain during the war,” said Tsuchihashi.

Shimazaki Shuzo has used the cave to store sake brewed in the city center since 1970. It named the historical site the “cave storehouse.”

The temperature averages around 10 degrees inside throughout the year.

The cave has three 100-meter-long tunnels and five crossing tunnels, which are 60 meters. The width varies between 3 and 4.5 meters, and the height is about 4 meters.

“We installed the lights, concrete floor and entrance doors,” an employee of Shimazaki Shuzo said. “But other than those, everything remains the same as in the past.”

About 130,000 bottles of sake, mainly 1.8-liter bottles, are placed over a space of about 2,500 square meters. The oldest sake dates from 1970.

Yuka Anzai, who was visiting here along with her family from Sakura in the prefecture, said she enjoyed visiting the cave.

“I wondered why it is cooler here than in limestone caves, without any ice or coolant,” she said. “It is very comfortable to stay here in the hot summer.”