Mt. Aso-san is located at the center of Aso-Kuju National Park in Kumamoto and Oita, which lies roughly in the center of Kyushu. 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 Gogaku) on the central plateau, including the active Mt. Naka-dake. Many hot spring villages, including Tarutama, Jigoku, Aso, and Yunotani, are located inside and outside Aso-Kuju National Park. The Aso Uchinomaki-onsen-kyo Hot Spring Village, with more than 100 hot springs, is the largest among them. The 1,506-meter-high summit of Mt. Naka-dake, one of the major volcanoes of the world, where the air is filled with the smell of sulfur, can be reached by a ropeway and car. It is the sole place in Japan where tourists at the summit can take a close-range look at the dynamic fumes rising from the crater, which extends about one kilometer north and south and about four kilometers east and west. Since it is an active volcano, shelter dugouts are provided around the crater. Pictures of the interior of the crater taken with two TV cameras at the crater can be seen, under the viewer's control with push buttons, in the Aso Volcano Museum. Kusasenri, covered with volcanic ash, is located on the northern mountainside of Mt. Eboshi-dake, where you can relax while seeing cows and horses grazing or by riding a horse (accompanied by an instructor).
The Nakadake Crater can be reached in a 30-40 minute bus ride from JR Aso Station. There is one bus about every 1-2 hours.