
Fukuoka-ken (Fukuoka prefecture) is the most populous prefecture of Kyushu, Japan with a population of over 5 million. The Aso caldera is the largest caldera in the world. Drive around the outside of the caldera; there are a few hills where you can get a spectacular 360-degree view of the caldera, the nearby mountain range, the cities within it, and Mt. Kujuu to the north. The Aso rim is probably one of the most breathtaking views in all of Kyushu.
If you know a Japanese person living in the area, get them to show you the natural spring inside the caldera which supplies fresh water to the region, the beautiful waterfalls at the local park, and the windmills around the caldera. Feel free to ignore Mount Aso itself as it is basically a smelly pit with muddy water at the bottom, and the steam coming out of it is toxic and dangerous to stand downwind of.
During the winter months, take a ride down a scenic canal in Yanagawa in one of 150 small "kotatsu-bune" boats. In the boat, you keep your legs covered with a "kotatsu" quilt, while sitting at a low table equipped with a charcoal braziers. During the ride you can often enjoy cups of hot sake and mikan citrus fruits, common to this area during the winter months.
The local speciality is a version of ramen made from boiled pork bones, known as tonkotsu ramen. It is widely available from a number of street stalls called yatai on the streets of Fukuoka City and Kurume, as well as at the Raumen Stadium in the Canal City entertainment complex.