One of the most lush and densely forested places we visited was the Fern Grotto. The only way to access it (at least for tourists, but perhaps also workers) was by boat. It is located in the the Wailua State Park, about 2 miles inland up the Wailua River (the only navigable river in Hawaii).
After we disembarked from the boat, we had a short hike through the rainforest to get to the grotto.
There we received a history of the grotto, including why we couldn’t get any closer (falling rock). It was at one time one of the most popular spots in Kauai for concerts and weddings. One of our guides happily offered to marry/re-marry anyone who so desired, and assured us all it was legal & binding.
After looking around and taking pictures to our hearts content, we wandered back down the path to our boat–as beautiful as it was, we had luaus to go, hulas to do, and pork to eat…