The Kosoyu is the showpiece public bath of Yamashiro Onsen, a careful 2010 recreation of the 1886 Meiji-era bathhouse that once stood on the same spot. The exterior is timber and tile with a tall central skylight; the interior is dim and atmospheric — a single octagonal bathing pool below stained-glass windows, paved with Kutani-ware tiles, with hot water piped from the source in the square outside. Bathers sit on small stone stools to wash, then soak in silence.
Upstairs is a small museum on the bathhouse's history and a tatami rest room where guests are served tea after their bath. The whole experience takes about an hour. Admission is around 500 yen, and tattoos are accepted (a rarity at Japanese onsen). The Kosoyu opens at 6am, which is the best time to visit — you may have the place to yourself for the first hour.