Fukuoka Prefecture is located on the island of Kyūshū at the northern tip of the island with the closest distance to main island Honshu across the Kanmon Straits. 18% of the land area of the prefecture is designated as natural parks . Nevertheless, the main cities form one of Japan's main industrial centers, accounting for nearly 40% of the economy of Kyūshū.
Right south of the city Kitakyushu is a forested mountain ridge, which is composed of limestone and karstified. It is known as カルスト高原 平尾台 (Karst plateau Hiraodai), named after the village Hiraodai. It is only 6 km long and 2 km wide. Here numerous caves are known, and four of them are show caves open to the public. So many show caves all at the same location works only if there are quite a lot of tourists and if every cave has a specialty. You can find a huge entrance pit and a cave where you wade in the cave river.
Not only the limestone is of interest here. There is also coal to be found in the sedimentary rocks. As Japan is a country with few resources, coal mining was of great importance, but eventually it became cheaper to buy on the world market. As a result the coal mining collapsed and the collieries were closed. The town Tagawa City has numerous coal mining related sights.