Sukayu Onsen Sennin Buro

The Hiba Sennin-buro (ヒバ千人風呂, literally "thousand-person bath") is a cavernous hall built entirely from Japanese hiba cedar, large enough to hold a hundred bathers at once. The water is strongly sulfurous, the smell hits you before you even step inside, and the steam fills the room densely enough that visibility across the hall is limited. The mixed-gender bathing area has a partitioned women's section for those who want the experience without full exposure. There's also a smaller separate-gender bath called Tama no Yu (玉の湯) for those who prefer it. This is one of the most storied traditional bath halls in the Tohoku region, on the slopes of Mount Hakkoda.