In Japan, Beppu is one of the most well-known places for onsen.
See, there is even a small fountain right in front of the train station. The hot water which is shot out consistantly from the small "crater" is real sulphuric spring water, know to have beneficial medicial effects.
A "Hell-Well" (地獄 aka JiKoKu) is actually a small crater where heated water/liquid keeps spitting out of it. This output is usually sulphuric. There are 8 famous JiKokus in Beppu, eg Sea Jikoku, Blood jikoku etc etc.. but we decided to go for only 1.
This is the Umi Jikoku (Sea Hell-Well). This one is called "Sea", because the liquid being spit out is blue in colour.
Nearby there is a place where u can soak your feet in the hot spring water.
Its really hot!
I secretly took pictures of other kids who soaked their feet too. If you look at the photos carefully, you will be able to see that the lower half of their legs are red.
Next stop in Beppu was to the famous MUD onsen bath. At this place called HoyoLand, they offer all kinds of mud bath - indoor and outdoor (mixed bath)
As the mud is know to have some therapeutic effect on the skin, its no wonder some of the onsen goers smeared mud all over their face.
Of course, due to the nature of mixed bath, no photography was allowed. I got these pictures from the internet.
It is really enjoyable to be able to soak in the warm onsen and admire at trees/nature/mountains around, at the same time...