Yunomine Onsen, a small valley town centered around an active hot spring. There is a spring right in the center of the town as well as multiple ryokan and hotels offering unique onsen experiences.
The last day from Koguchi to Kumano Naichi Taisha is quite a trek up and down, and then up and down again over numerous cobblestone steps that are slick with moss. It is beautiful, but it is also treacherous on rainy days.