Akiyoshido Cave (秋芳洞) is Japan's longest and largest limestone cave.
Best visited by car, but accessible by bus.
The pedestrian thoroughfare that connects the entrance of Akiyoshi Cave to restaurants, shopping, parking and the bus center is a 40-minute bus ride (1,170 yen, 1 per hour) from the Shin-Yamaguchi Shinkansen station or a 60-minute bus ride (1,210 yen, 1 per 2 hours) from Yamaguchi Station, both in Yamaguchi City.
From Mine Station, it’s a 25-minute bus ride (200 yen, 1 every 90 minutes). There's also a "Karst Taxi" service for transport in and around the park.