The karst formation of Hiraodai is said to have over 200 caves, and of these, three have been open for tourists to enter without special attire. A must-see is the Senbutsu Limestone Cave with 30 stalactites hanging from the cave ceiling in the entrance. The cave is designated as a national natural monument. Upon proceeding 480m you start splashing as you walk down a stream, feeling like a real explorer. The Mejiro Limestone Cave has one of Japan’s largest monoliths, at around 20m. Everyone from beginners to experts can go caving here, so if you are interested please ask at the reception. Ojika Limestone Cave is known as the “Dinosaur Trap”, having a vertical shaft for an entrance which is unusual in Japan. Upon descending 25m the underground streams flow through the caves, giving a clear picture of the karst formation. Fossils of the Japanese river otter, Mukashi Japanese deer and the Naumann elephant (Palaeoloxodon naumanni)  have been discovered in this cave.