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Photo: Thomas Stepleton, Public domain via Wikimedia Commons
Towards the southern end of Akiyoshidai is the Akiyoshido cave, named by Emperor Hirohito in 1926 when he was crown prince. This cave is up to 100 m wide and has almost 9 km of passages, making it the longest in Japan and one of the longest in Asia. An approximately 1 km-long section of the cave is open to the public as a sightseeing course, with a walkway and bridge system, entering at the cave's lowest point and exiting by an artificial elevator. This portion of the cave is also well decorated with a variety of large and colorful speleothems. Akiyoshi Cave and the main observatory can be reached on foot, but cars or "karst taxis" are necessary to reach other caves. A one-day taxi pass costs ¥800.
Akiyoshidai Kokutei Kōen (秋吉台国定公園) is a Quasi-National Park in Yamaguchi Prefecture, Japan. It was founded on 1 November 1955 and has an area of 45.02 km².
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秋吉台国定公園
includes the Akiyoshidai (秋吉台, Akiyoshi plateau) and Japan’s longest cave, the Akiyoshido (秋芳洞), the latter of which is designated a Special Natural Monument. Akiyoshidai is served by a natural history museum, visitor center, rest house, youth hostel and park headquarters building, and is traversed by a scenic roadway and several walking trails. Events include a fireworks festival in July, a “Karst Walk” in November, and an annual burning off of dry grasses in February called Yamayaki. Akiyoshidai is a part of the largest karst topography in Japan. The park is best reached by direct bus from Shin-Yamaguchi Station, though there is also service from JR Yamaguchi Station, Hagi, and Shimonoseki.