The thermal springs of Zao Onsen, whose water is acidic and high in sulphur, have been recognised throughout Japan for centuries due to their therapeutic virtues, particularly for skin disorders (leading to the nickname of "source of beauty"). This enormous open-air bath on the mountainside blends in beautifully with the surrounding countryside. Once you get used to the strong smell of sulphur and milky water, which can be off-putting, you will be ready to enjoy a 100% authentic Japanese experience!