You'll smell Jigoku-dani before you see it: waves of sulphur roll through the air as you approach this hissing, steaming volcanic valley above Noboribetsu Onsen. A wooden boardwalk leads you past bubbling mud pits and mineral-crusted vents to a boiling geyser, the landscape so otherworldly it genuinely looks like a portal to the underworld. According to local legend, the demon Yukujin makes his home here, though he's a kindly one who bestows good luck. You'll find statues of him grinning from corners all over town. It's raw geological drama at its most accessible.