Ramune Ginsen is one of Japan''s premier natural carbonated hot springs, located in the town of Tonbara within Iinan Town, Iishi District, Shimane Prefecture. Nestled in the mountainous interior of the Chugoku Range near the border of Hiroshima and Shimane prefectures, Iinan Town sits on a plateau at roughly 450 meters elevation, surrounded by lush countryside. The spring traces its origins to a therapeutic bathhouse called Shiogakuchi Onsen that operated here during the Meiji era. In 1881, the mineral water earned an award at the World Exposition in Germany, and during the Meiji period, it was bottled and exported worldwide as a natural carbonated drinking water.

The spring is classified as a carbon dioxide-sodium-bicarbonate/chloride cold mineral spring, with a source temperature of approximately 15 degrees Celsius. It contains over 1,040 ppm of carbon dioxide gas and more than 1,260 ppm of bicarbonate ions, making it an exceptionally rare spring in Japan that simultaneously possesses the contrasting properties of both a carbon dioxide spring and a bicarbonate spring at high concentrations. The mildly acidic water is gentle on the skin and is known as a beauty spring. The source water is colorless and transparent, but upon exposure to air, it undergoes a mysterious transformation from clear to green, then yellow, and finally orange. The water is provided as free-flowing source water, heated to a comfortable 38 to 40 degrees Celsius for extended soaking.

Facilities include a main bath, a private bath featuring a traditional Goemon-buro iron cauldron tub, and a large barrier-free bath accessible to visitors with mobility needs. Admission is 600 yen for adults, 300 yen for elementary and middle school students, and free for infants. Private baths are available at 2,400 yen per hour by reservation. Operating hours are 11:00 to 20:00, closed every Thursday. Free parking is available for 15 to 20 vehicles.