Mt. Aso-san, the largest active volcano in Japan and among the largest in the world, is located at the center of Aso-Kuju National Park in Kumamoto and Oita, which lies roughly in the center of Kyushu.
The summit is 1592 m above sea level.
Its caldera is 25 km across north to south and 18 km across east to west.
The mountain is a typical complex volcano composed of an outer rim with a total circumferential length of 128 kilometers, a caldera (circular volcanic basin) with three municipals inside, and five mountains (Aso Gotake) on the central plain.