the hundred plates close-up, akiyoshi cave

adventure akiyoshi akiyoshido akiyoshidou ancient asia cave cavern dam dark destination dripping earth flowstone formation geology historic honshu hundred hyakumaizara inside japan japans karst known largest limestone mine monument mystic natural nature park plates rimstone rock saucers scenic science solutional special speleology speleothem spills stone this time tourist underground view walls water yamaguchi