Oniyama Jigoku is one of Beppu's famous hells, a boiling-hot spring attraction in Kannawa where the steam, mineral water, and slightly eccentric presentation are all part of the experience. Its nickname, the crocodile hell, comes from the crocodiles kept on site, warmed by the geothermal heat that rises constantly through the grounds.
It is not as beautiful as Umi Jigoku or as visually startling as Chinoike Jigoku, but it adds variety to the circuit and shows the older entertainment side of Beppu's hot spring culture. Visit it as part of the multi-hell route rather than on its own, and expect a compact, quirky stop with plenty of steam.