The first jigoku we visited was called Umi Jikoku, or "Sea Hell". It's called so because of the cobalt-blue waters and the 200˚C waters where they boil eggs for visitors to try.
Temperatures are so warm that this tropical water lily is able to live nearby.
This was probably the most interesting Jigoku because it had the most to see and do. Here was a nice dragon to take my photo with and they also had a free foot bath area.
In the same Jigoku area at Umi Jigoku they had a red water pool as well. Small, but nice.
After Umi Jigoku, we took a bus down to Chinoike Jigoku or "Blood Pond Hell". This is the oldest natural Jigoku in Japan, and it gets it's red color from clay that is dissolved in the water. This Jigoku was rather lame, not much to see and too many people to get into the free foot bath here. Not sure if it was really worth my 400 yen...
After Chinoike Jigoku we went next door to see Tatsumaki Jigoku or "Water Spout Hell". Here there is a geyser that shoots up every 25 minutes, supposedly to a height of 20 meters. Unfortunately, they built a cover over it, so you can't actually see how high it would go, as it stops at about 10 meters and hits a ceiling. Whoever thought up that grand scheme was not the brightest bulb out there...
Anyway, there are ten Jigoku in total, but we only saw these three. That was about enough for me for one day. They were cool to see, but the price vs. entertainment value was definatly the limiting factor for me. Cool, but 400 yen (more than $4.00 per site per person) was a bit steep for me. If you plan on going up here though, I highly recommend getting the day bus pass from the tourist information center at Beppu train station. You can take the bus up quite high and walk down, there's more to see up here than just the Jigoku. There are lots of onsen, restaurants museums and views. 900 yen is a super bargain for the bus if you plan on taking it up and down and around. If you ride the bus at least 3 times then you're saving money.