Plentiful hot (and sometimes cold) springs, called onsens, are scattered throughout the volcanic mountains of Hokkaido. Almost all require that men and women stay in separate areas and for visitors to take dips strictly in their birthday suits. Hotel sentos in Sapporo and Rusutsu are a great taste of Japanese bathing culture, but the real-deal, mineralrich onsens in small villages and mountain corners are worth seeking out after a day of skiing. Got ink? Be sure to ask each onsen about its tattoo policy before paying, or seek out kashikiri-buro, private baths that are suitable for tattoos and those uncomfortable with nude bathing around strangers.