I visited all of the hells of Beppu over the course of three days. Each of them offers something remarkably different to the last. My favourite titled of the eight was, 'Bloody Hell', but the highlight overall was Crocodile Hell during feeding time. I have never seen crocodiles before, so watching them devour meat with aggression, was a nice first introduction to those otherwise peaceful creatures.
If you visit Beppu for any reason, the eight hells are well worth a visit, and the one day pass allows you to complete all eight in a day for a much lower price.
Hells of Beppu
Go on a tour of the different hot springs. Feel the hot steam and see the water bubbling up from underground.