Otaki-no-yu

The draw here is the awase-yu, a set of five linked tubs in the men's bath where the source runs from one to the next and cools as it goes. You start in the coolest and work up, the old Kusatsu way of getting used to the heat, and the hottest tub is the cloudiest. The women's awase-yu has a different, more Western-styled room. Outside, a hot waterfall pours into the open-air pool, and the bath's name is said to come from that fall.

Plan a visit for the second or fourth Saturday morning if you can. That is when staff drag a rope through the supply pipes to clear the mineral build-up, and the normally clear Nikawa water turns milky, clearing again as the day goes on. The building has a restaurant, a cafe and a big tatami rest room in the basement, so it works for a whole wet afternoon.