Tateno Gorge
Although the Aso caldera is now covered in fertile grasslands, between 10,000 and 6,000 years ago it was filled by a large lake. Over time, the water drained away through Tateno Gorge, the only gap in the caldera’s high walls, leaving the open expanse we see today.
Legend says the founding deity of Aso, Takeiwatatsu no Mikoto, kicked the caldera wall down in order to drain the area and make it possible to farm rice. Geologically, the drainage is thought to have been caused by a seismic fault beneath the gorge.
Looking down, one can see where Aso’s two main rivers, the northern Kurokawa and the southern Shirakawa, merge and flow out of the caldera toward Kumamoto. In autumn, the changing leaves paint the gorge with shades of red, yellow, and orange.