Fukui is a prefecture located in the Chūbu region of Honshū island, the biggest island of Japan, in the middle on the coast towards China. It is famous for the Lower Cretaceous Kitadani Formation, sedimentary rocks full of dinosaur fossils, and so the most important geological sight of the prefecture is the unique dinosaur museum. Numerous dinosaurs were named after their type locale, like Fukuiraptor, Fukuisaurus, Nipponosaurus, Koshisaurus, Fukuivenator, Fukuititan and Tambatitanis. Quite funny those names, actually.
The prefecture has mountains and sedimentary rocks, however, there are not many caves. In the old list of the WEC a cave named 白馬洞 (Hakuba Cave) was listed which was probably open in the 1980s, but today there is no underground site open for tourists.