Kyusendo is a limestone cave in Hitoyoshi. The limestone layer was repositioned and uplifted from the ocean three hundred million years ago. During that time rain water containing carbon dioxide penetrated and eroded the limestone on its way to the Kuma River. The cave was discovered in 1973 and being 4.8 km long, it is the longest cave in Kyushu, with 800 meters opened for public.
The back of the ticket office marks the entrance of the cave. The combination of the lukewarm wind from the cave, a sign saying "Be aware of bats" and the dim tunnel made me flinch, but I went ahead regardless.
Inside was dim and damp and it felt like the inside of an underground mine. The lights on the ground marked the path ahead, but be sure to have appropriate footwear as it can be slippery in parts. The low ceiling passage reminded me of Coober Pedy in Australia, where homes are built underground to avoid the heat from the desert. Suddenly, I was plunged into the darkness, felt a space opening above my head and heard the sound of water. I got used to the darkness after a while and found the river far below me. I was again scared because of the dark ceiling above my head and black river under where I was standing. You'd see stalactites, stalagmites and stone pillars which linked these two with some explanations (only Japanese). The stalactites and stalagmites grow 1 mm per year. Nature's timing is mind boggling. When you come back here 20 years later, they would be only 2 cm longer. I found it funny that almost everyone asked, "How long will it be from here?" in the cave. I don't know who told me that bats pick up your hair, so I automatically covered my head when I saw them from place to place.
There are two courses to choose from in Kyusendo - general course (ippan) and adventure course (tanken). You would need to wear a helmet, a head-light and gum boots for adventure course, so I guess it would be harder but more exciting. The general course on the other hand takes approximately 30 mins to 40 mins. Access to Kyusendo is 20 mins drive from Ashikita Kita Interchange or 15 mins walk from JR Kyusendo Station.