Welcome to one of Beppu's most stunning sights, Umi Jigoku, or the "Sea Hell." You'll be mesmerized by the almost unreal, steaming cobalt-blue pond—it's a sight you won't forget, with water temperatures reaching a boiling 98°C. Take a relaxing stroll through the beautifully kept grounds, which include a tropical greenhouse and a smaller, reddish hell, and don't leave without trying the onsen-steamed eggs and pudding. For a perfect break, dip your feet in the free footbath on-site; it's a wonderful way to soak in the unique atmosphere.