Funaoka onsen is not technically an onsen, since the water for the baths is heated in the building and not drawn from a geothermal spring. The Japanese government, however, allowed the bathhouse to use the word "onsen" in its name in 1933 due to the presence of the country's very first electric bath. 

Electric baths, while not originating in Japan, are used as therapeutic devices in many public bathhouses throughout the country. It serves well to memorize the symbol for electricity (電気) so that you don't shock yourself accidentally! Funaoka onsen offers several other baths, including an herbal bath, a traditional cypress-lined tub, an extra-hot bath, as well as two outdoor baths, one hot and one cold. 

Before you make it to the bathing section, have a good look around the changing room; separating the men's side and the women's side are carved wooden panels near the top of the wall, with depictions of cannons and cavalry. Dating from the pre-WWII invasion and occupation of Manchuria (present-day northeastern China), they have remained there since despite the terrible history surrounding Japanese empirical aspirations. 

Other wooden carvings around the room are less dramatic but no less detailed; some of them required 10 years to be completed. The latticed ceiling also incorporates a wooden sculpture of a tengu, a spirit with a long red nose that you may recognize from your phone's 👺  emoji.

When making your way to the baths proper, be prepared for a change of decor as the passageway is tiled with handpainted Majolica tiles, a traditional Spanish ceramic known for bright, vibrant colors and textured surfaces.