Akiyoshidai is a very famous part of the Yamaguchi Prefecture, and also a very popular excursion for people who live in Japan. However, for those who are only passing through, it may not be the first recommendation that they receive for an adventure, which is a shame, because the Akiyoshi-do cave is the longest cave in Japan, and also one of the biggest caves in the Orient. If you have been inside a cave before this will be a fantastic experience. If you have never been inside a cave before, then get ready for a really cool, and somewhat creepy, stroll through darkness, underground streams, and beautiful stone formations.