"Jigokudani hotspring in Nagano Japan 001" by Yosemite.
Licensed under CC BY-SA 3.0 via Wikimedia Commons.

So I heard about Hell Valley Monkey Park ( 何で Hell Valley と言うんですか????), the natural hot springs patronized by Japanese macaques in the colder months of winter.

I kind of want to go, but wow, it's a three-hour ride by shinkansen.