Yunokawa Onsen is Hokkaido's oldest hot spring resort, located on the eastern edge of Hakodate where the Matsukura River meets the sea. The hot spring district has been welcoming visitors since the 17th century, and the water — alkaline bicarbonate sodium, around 47°C — has a notably soft, smooth quality good for the skin. Several of Hakodate's larger ryokan and hotel onsen facilities are concentrated here, and the public bath houses are straightforwardly inexpensive.
The area is pleasant for an evening if you want to combine onsen soaking with a walk by the sea. Tram line 2 from central Hakodate runs directly to the onsen area (about 20 minutes from the station), making it an easy excursion at the end of a day exploring the Motomachi slopes or Goryōkaku. The hot springs area is also known for a troop of wild monkeys that takes to the hot spring pools in winter — a sight that has made this small resort briefly famous in viral media.