The hot springs in Yudai Mountain are cold water springs, which are indeed underground springs. It's heated. Men and women bathe separately. The hot spring is on the second floor. The first floor is a special health pavilion, and the third floor is a lounge. Everything is together except taking a shower. What feels more distinctive is the various characteristic pavilions on the first floor, probably modeled after Japan. Yudaishan Hot Spring is the only Japanese hot spring, which is worth visiting. It's different from Tianmu Tongbo.