Within the Akiyoshi-dai Quasi-National Park, the rolling Akiyoshi-dai tablelands are dotted with curious rock spires, beneath which are hundreds of limestone caverns. One of these is Akiyoshi-dō, the largest limestone cave in Japan.
It is size that makes the cave impressive. It extends about 10km, at some points 100m wide (though public access is limited to a 1km section), and a river flows through it. The watery reflection of the towering cave walls at times gives the dizzying impression you're walking over a deep ravine. But you can leave the spelunking gear at home – there's a paved route, regular push-button information points that belt out explanations in various languages, and an elevator in the middle that takes you up to a lookout. Despite the development, Akiyoshi-dō is a good side trip from Yamaguchi or Hagi, or a stop en route between the two.
For more on the cave and the surrounding plateau region, a great area for nature walks, go to www.karusuto.com. Information is also available at tourist offices in Yamaguchi and Hagi.