Iwamuro Onsen Yorinare
A city-run day spa (Niigata City Iwamuro Health Promotion Centre) at Iwamuro Onsen, a spa at the eastern foot of Mt. Yahiko in Niigata's Nishikan ward, often called 'Niigata's back parlour'. Set on a rise at the edge of the spa town, its main bath and open-air bath look out over the Echigo plain toward Mt. Kakuda and Mt. Yahiko. The indoor pool is heated tap water, but the small rock-lined outdoor tub is fed with rich, free-flowing sulfur-bearing sodium-calcium chloride spring (hypertonic, mildly alkaline) whose faint sulfur scent and floating mineral flakes feel unmistakably like real onsen. Admission is ¥650 for adults and ¥390 for children, and a face and bath towel set is included, so arrive empty-handed. Open 10:00–20:00 (last entry 19:30), closed the second and fourth Wednesdays (next day if a holiday) and 29 December to 3 January. An upstairs lounge allows re-entry, and there are rental rooms and a snack corner; free parking for 80 cars. About 10 minutes by car from Iwamuro Station on the JR Echigo Line or 20 minutes from Maki-Katahigashi IC. Pair it with Yahiko Shrine and Niigata's sake breweries.