Having previously visited Iceland, I found the Hells of Beppu quite underwhelming. It had more of a theme park vibe rather than natural beauty. We bought the combined ticket to visit all 7 hells and out of all of them, for me, only Umi Jigoku was wow. I was most disappointed with they geyser at Tatsumaki Jigoku (tornado hell). The top of it has a stone mantle so it doesn’t shoot up very high. The entrance price is very reasonable and savings to be had when buying the combined ticket. You need cash to buy any snacks or drinks in the hells (no suica or other cards accepted). I can recommend the steamed sweet potato cakes and the sweet potato ice cream. We visited ourselves by local bus (very easy) rather than a tour but found the directions for some of the hells not very clear or obvious. There were also free hot spring foot baths in a couple of the hells which was lovely after a lot of walking. An interesting place to visit but not what I expected based on articles I’d read beforehand.