Numanotaira Crater

About 1.2 kilometers across and 150 meters deep, northwest of Mount Adatara's peak. Descending inside is prohibited due to volcanic activity and toxic fumes. In 1900, an eruption destroyed a sulfur refinery on the mountain and killed 72 miners. The closest viewpoint with a clear look into the crater is a 15-minute walk north from the peak along a broad ridge called the Ox's Back, where the interior gradually comes into view, largely bare of vegetation. A trail circles the full crater in 7.4 kilometers, taking three to four hours, though most visitors walk out and back with an optional detour north to Mount Tetsu.