Akiyoshido Cave (秋芳洞) is Japan's longest and largest limestone cave.
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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.