Dogo onsen is one of the oldest and most famous onsens in Japan. Legend has it that many many years ago an egret injured its leg and soaked it in the hot spring every day until it was healed. People who watched this also soaked in the hot spring and regained health.
The onsen building is three stories tall, with the baths on the first level and lounges above. There is one bath room reserved for the exclusive use of the emperor, although the public is able to pay for a tour of that area. The basic entrance for the bath only is 410 yen. I opted for the 840 yen entrance which included the second floor lounge area, use of a yukata, and a tea and cookie snack after the bath. There are two higher levels of entrance fee - I think they include a different lounge area and maybe a bigger snack. I also had to buy a little bar of soap for 40 yen.
Of course, photos are not allowed in the bathing area, but I can tell you it was a very small, crowded indoor bath. I'm glad I went because of the history, but I probably wouldn't go on a regular basis, unless maybe I was ill and believed in the healing powers of this onsen.