While the main feature is considered to be in the middle of town, this area is my favorite spot in Kusatsu Onsen. Here you can take off your shoes and stroll up a hot spring river. It's a perfect activity for a cold winter night and believe me, Kusatsu can get cold!
Once you reach the end of the walk there is a large public onsen which is also really great. Don't miss this area if you visit Kusatsu!