国指定特別天然記念物。国定公園。ラムサール条約登録湿地。日本地質百選。
秋吉台南側山麓に開口する総延長8,790ｍ（国内4位）の鍾乳洞で、容積は日本最大規模。洞窟内には百枚皿（石灰華段丘）や黄金柱（石灰華柱）などの洞窟生成物が発達する。
シコクヨコエビなど洞窟特有の生物が生息しているほか、5～8月にはコウモリもみることができる。
Akiyoshi-do cave, a limestone cave with total length of 8790 m, has the greatest capacity in Japan. First, it was formed as a phreatic cave one million and several hundred thousand years ago. The capacity then increased gradually by the repeated fall of the roof and the dissolution of limestone. Various speleothems and cave formations have developed in this cave, such as rimstone pools (Hyakumai-zara) and flowstones (Ougon-chu). Furthermore, many underground creatures have been identified in the cave and the surrounding areas.
