I just got back from a little trip to the Oita area. I had the pleasure of stopping by Shichirida Onsen, which is known for its naturally carbonated hot spring water. The photo is one I took from a web page about a similar onsen but it accurately shows the way my arms and legs looked in the spring water. The onsen itself is not fancy at all but the spring water is quite unique and, in my opinion, worth a visit if you like onsen. The temperature is not very high so it’s good for a nice long soak.
The following web page is in Japanese but even if you don’t read the language, I think the pictures will give you an idea of what to expect and the Google map will help you find it.
– Kirk