The Ryuga Cave is a roughly 4-km limestone cave which took approximately 175 million years to form. It is one of Japan’s best-known limestone caves and designated by the government as a natural monument/historical site. About a 1-km part of the cave is open to the public and you can view some mysterious scenes there.
Near the exit are the remains of cave-dwelling communities during the prehistoric Yayoi period (from around the mid-3rd century BC to the mid-3rd century AD). In particular, Yayoi earthenware covered with calcareous sinter, known as “a divine pot,” is extremely rare and an echo of an ancient world.
A recommended route is the “Adventure Course,” which is so small that you must kneel down to go forward while relying solely on a headlight. At the Chincho (Rare Birds) Center that is adjacent to the cave, you can see long-tailed cocks, designated by the government as a special natural treasure.