Takinoyu (Aizu Nishiyama Onsen)

A long-established ryokan in the Oku-Aizu mountains, drawing from two separate springs, Takinoyu and the wilder Arayu, both delivered as 100% kakenagashi (源泉掛け流し). One is alkaline with a faint sulfur edge, the other saltier; the baths alternate or run separately so you can experience both. The open-air bath is mixed, though women have it to themselves during evening hours. Founded in 1899, the inn sits at the far end of Nishiyama's cluster of eight springs, with the sound of the river audible from the rooms.