The Fern Grotto is a cave along the Wailua River on the island of Kauai, Hawaii. It’s the destination of the flat-bottomed boats that cruise the river. Passengers disembark and walk along a path through luxuriant jungle foliage to reach the grotto, as this Japanese group has done. There they stand and listen to “traditional” Hawaiian music, until it’s time to make way for the next herd of tourists.
This picture shows the Fern Grotto as it appeared when I visited it in 1986. In 1992, Hurricane Iniki did extensive damage to much of Kauai. The grotto apparently still has not fully recovered its ferns and jungle surroundings.