Zao Onsen is one of the top spots for strong acidic hot springs in Japan.Its springs are sometimes even called the "Springs of Beauty”.
Zao Onsen is the source of strong acidic sulfur springs, said to help with rejuvenating and strengthening the skin and blood vessels.
The skin and blood vessel rejuvenation and skin beautifying effects of Zao Onsen are the reason why it is also called the "Springs of Beauty".