Nango Valley
The Nango Valley lies in the southern part of the Aso caldera, between Aso’s five peaks and the caldera wall. The 23-square-kilometer valley has natural terraces that lie along the banks of the Shirakawa River. These terraces are thought to have been formed by multiple lava flows that entered Tateno Gorge, which lies further downriver.
Water from the Shirakawa River flows out of the caldera through Tateno Gorge, the only opening in the Aso caldera wall. Long ago, when lava flowed into the gorge, it partially blocked the water from exiting the caldera. The resulting blockage is thought to have created these natural terraces.
The Nango Valley also has grasslands for grazing livestock at the foot of Mt. Nakadake and the slope of the caldera wall, and fields for cultivating low-temperature-resistant vegetables at the foot of Mt. Nekodake. The western section of the valley has numerous onsen.