Location: Beppu Hells: I went to hells.
The hot springs are so hot they've been given the name hells in English - though that moniker is certainly used for attracting tourists as much as describing the temperature. In Japanese, the term is jigoku, and there are eight total. Six are clustered together in Kannawa,with two more side-by-side a short bus ride away.
Because the hells are such a big draw, they have become quite touristy, which can be a turn-off for some visitors. However, with a little constructive photo cropping and a blind eye, you can ignore most of it. One of the hells has a small zoo, but it certainly is hell for this elephant.
I'd like to return to Beppu or somewhere similar to enjoy another (hopefully longer) sand bath, a mud bath, and some of the other sauna-style treatments one can find in town. Beppu is good for a full day (or two if you really want to see it all and take several baths). Lodging will be a bit more expensive since it's a tourist town, but visitors can use Oita (a short train ride away) if only staying for a day and they don't want to stay in a ryokan or in town.
The hells are accessible by several buses which leave very frequently from the train station. Ask at the visitor center/tourist information desk for a current schedule (buses 5, 7, and 9 are fastest) and a map. Remember that two of the eight hells are a second 5-minute bus ride away (route 16 or 16A from the Kannawa hells). Each hell charges 400 yen for admission, or you can buy a souvenir ticket book for 2000 yen that admits you to all eight hells. They're open every day from 8 AM to 5 PM.