Japanese onsens, or public  baths, are rarely empty making it difficult to get pictures of the inside of one. Luckily we went to one just as it opened so here are some pictures. Some onsens use the Japanese word for hot water, which is one character pronounced "you", spelled Yu in Japanese:

A general shot of most of the room. The large bath to the left will be really hot. The round pool in the middle would probably be warm, right in the really comfortable range. The quarter circle pool to the right would be cool if not cold. They are usually 2 feet deep or so and have a bench along the edges. Before entering the onsen, one comes to the shower area and grabs a stool. You sit facing the mirror and first turn the knob to test the temp of the water, if that option is available. Then you press the shower button and water comes from the moveable shower head. You completely clean yourself head to toe, at least three times.
There is usually an "authentic" bath, even when the places are in the middle of a city. This one is average. I have seen much nicer rocked baths with caves and what not. A bigger shot of the large bath and the water pump that constantly keeps hot water in the bath.

 

Ryan McDonald 2005, for information about using images or text please click here.