Close to Sapporo and boasting 100% real onsen water, this restaurant/onsen establishment features dark brown water, several uchiburo, and a large rotenburo with views of the surrounding hills.
A pleasant diversion from the hotels and spas of nearby Jouzankei, Houheikyou Onsen offers a much more authentic experience for those needing a quick escape from Sapporo. It's within walking distance (20 minutes or so) of the main Jouzankei bus stop, but a taxi might save time. Check the bus schedules carefully -- some buses go as far as Houheikyou before turning back, and a good route for day trippers is to take those buses as far as Houheikyou, walk to Jouzankei, and return from there by bus to Sapporo after the soaking is done.