Iokido Cave is a mysterious cave located in Aki City, Kochi Prefecture, and is designated as a national natural monument. It is a mysterious cave with a fern community. It is located in the eroded old strata of the earth that was deposited about 3.1 million to 2.3 million years ago (Pliocene to Pleistocene epochs). About 40 kinds of rare ferns grow naturally in the old eroded strata. The inside of the cave is so cool that it is called a "natural cooler", and it is enveloped in a fantastic atmosphere as if you have wandered into an ancient forest. Due to its unique scenery, it has become popular as a spot for SNS in recent years.

The greatest attraction of this cave is its unique ecosystem and the fact that you can experience a mysterious space. As you go deeper into the cave from the entrance, cool air drifts and the green of ferns spreads all over the walls. In particular, Iokido Cave is an experience unique to being able to observe precious ferns that can only grow in humid environments up close. From the back of the cave, even more mysterious light shines in, captivating visitors.

Iokido Cave is not just a place to enjoy the scenery, but also a place where you can feel the mystery of nature and the power of life. The cave is relatively safe as you walk on well-maintained footing, but caution is required as there are some slippery areas.

The normal course takes about 40 minutes on foot, with a turnaround at a point about 200m from the cave entrance. The adventure course turns around about 400m from the cave entrance.