Unzen

While Japanese 'hells' (jigoku) are given these names due to the barren and smelly landscape created by the sulfuric gases they emit, the Unzen Hells have a unique history that makes them truly hellish. From 1627 to 1630, the Unzen Hells were used by the government to torture Christians by lowering them into the boiling waters in an attempt to get them to denounce their faith. Thirty-three of these martyrs died here as a result of the torture. The cross jutting out of the hellscape was placed here in the late 19th century to honor those victims.

An active volcanic group of several overlapping stratovolcanoes.

A highly acidic sulfuric hot spring. In addition to sulfur, the mineral content includes aluminum, iron, and sulfate. The water temperature is 98 °C, and the hot carbonate and hydrogen sulfide gasses that erupt from the springs can be as high as 120 °C.

The hot spring system known for having the hottest and most active springs in Japan, with some of them reaching 80-105 °C and producing over 15,000 tons of hot water daily. The hot spring system consists of 30 individual springs.