The reason Kusatsu is so popular is because of the of the onsen. I suppose I should explain what onsen is. 温泉(onsen) is a natural hot spring in which people bathe. The minerals in the water are supposed to cure illnesses, making onsen bathing a rejuvenating and relaxing experience.
Kusatsu is in the mountains of Gunma. It took us about three hours to get there on the train. There is a large hot spring source in Kusatsu that exists due to an active volcano right next to the town. The primary onsen source comes up right in the center of town. It is called ゆばたけ(yubatake).
|ゆばたけ 温泉 (yubatake onsen)|
There are a couple of very famous onsen facilities in Kusatsu. We checked out a couple. If you are shy, you just have to get over that. Because everyone is naked. Genders are, of course, separate. We mostly stuck to the private onsens in our Ryokan (a traditional Japanese hotel). They were gorgeous.