Kauaʻi, often referred to as the Garden Isle, has a huge number of outdoor attractions and activities that exemplify the island’s natural beauty for visitors to choose from. From the stunning Napali Coast to Waimea Canyon, it’s almost impossible for travelers to plan the perfect itinerary to see all the island has to offer. But you don’t want to miss this magical, fern covered grotto. Located along the Wailua River, you’ll have to catch a ride on a local boat or kayak tour to see the spectacle, but it’s well worth the effort and the perfect way to see why Kauaʻi has earned the moniker of “Garden Isle.”

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Formed of lava rock, the Wailua River area is home to a host of heiau (ancient Hawaiian temples and places of worship) and sacred sites, and the fern grotto is no exception. Cooled by waterfalls and fringed by kupukupu fern, the area was once limited to aliʻi (Hawaiian royalty) who visited the grotto to leave offerings for Lono, the Hawaiian god of agriculture. In more recent history, however, the grotto has opened up and become a visitor favorite. Starting with a single small rowboat and a borrowed motor in 1946, countless passengers have seen the grotto over the years, with local musicians performing in the natural amphitheater and weddings happening in the natural oasis.

So how can you see the grotto for yourself? Smith’s Fern Grotto Tour is well regarded by visitors and locals looking to see the iconic piece of nature, and the tour is perfect for families and keiki (kids). On the two-mile boat cruise, you can expect to hear songs and tales of ancient Hawaiʻi, and about the area itself. For four generations the Smith family has conducted these tours and have always had a keen interest in sharing the culture and heritage of Kauaʻi to the public.

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A great aspect of Smith’s Fern Grotto Tour is the vessel that ferries its participants up the river. Powered by a rear-engine system purportedly invented by family patriarch Walter Smith, Sr, the boat can open its deck and provide riders with a spacious, open-air experience that allows for excellent views of the trip upstream for the entirety of the ride.

It’s not a boat ride all the way to the fern grotto, however. To see the natural wonder for yourself, you’ll have to make a short trek on foot through a lush rainforest—doesn’t sound so bad, does it?—before reaching a small wooden viewing area of the lava rock cavern. Here, you’ll be treated to a wonderful and culturally enriching experience hosted by your tour operators, and may even learn a bit of hula from a cousin or relative of the Smith family—all while taking in the view of the fern covered grotto surrounded by exotic native Hawaiian plants.

The entire tour—roundtrip—takes one hour and 20 minutes. Tickets are $30 for adults, $15 for children ages 2 to 12, and free for keiki under 2. Find out more on the Smith’s website.