Of all Beppu's "hells," the Oniishi Bozu might be the most hypnotic - those gray mud bubbles popping up really do look like little monk heads bobbing in the pool! While some of the other hells might be more colorful, there's something weirdly fascinating about watching this thick gray mud rhythmically bubbling and plopping.

The foot bath here is a winner too. After walking around all the hells, being able to soak your feet while watching those mud bubbles pop is pretty perfect. Plus, the garden setting with cherry blossoms (if you time it right) adds that extra touch of beauty to contrast with the hellish mud pools.