Unzen Jigoku (Unzen Hell) — Active Volcanic Vents

Unzen Jigoku is a 500-meter-wide field of active volcanic vents on the slopes of Mt. Unzen, emitting sulfurous steam at temperatures exceeding 100°C from dozens of openings in the white mineral-crusted earth. The landscape — dead trees, bubbling mud pools, yellow sulfur deposits — evokes the Buddhist concept of hell, hence the name. The trails allow visitors to walk within meters of the active vents; the smell of sulfur is overwhelming.

Historically, Unzen Jigoku was used as an execution site during the Christian persecution — believers were scalded in the boiling pools as torture and execution. Monuments along the trail mark the martyrdom sites.