The Oimachi branch of the famous chain onsen. Not the most peaceful onsen due to its convenient location and general popularity, but certainly a place where one could spend the entire day relaxing and enjoying the baths and facilities. Note that it is not a natural onsen. Instead nutrients and minerals have been artificially added to the water.
There is the usual variety of baths for which the chain-onsen is known, from carbonated tubs and salt baths to jet baths and sleeping stone baths. If you wanted to get a taste of all that a Japanese onsen might offer, then this is the place. The bathing area is not all that large, however, and feels even more cramped during peak hours.
The ganbanyoku or hot stone spa (additional charge) is also a good experience. There are four rooms in total, set at different temperatures and with different surfaces on which to lie (small pebbles, flat rock, and seats for the cold room). The hottest is set at around 55°C—more than enough to have your pores seeping sweat within 10 minutes.
The facilities also include a restaurant/dining area, small bar, relaxation and reading lounge, massage chairs, and body care and aesthetic services.