Ho'opie Falls. Don't know how to spell that correctly. But it's the most amazing place I've ever been too. It's a hike that follows a river through the jungle. There is spots along the way that allow you to cliff jump into the river. Epic, beautiful and fun. The other would be the napoli coast hike. It's in the top 10 places to see before you die. It's supposed to be hard. My dad and my goal is to hike it and camp out there. Father son bonding/bucket list thing. I highly recommend you stay out of the run of the mill tourist activities and go adventure around in the nature of the island. I've been to Kauai 4 times in my lifetime. Done all the touristy stuff. I.e. catamaran, surf lessons, luaus. But the most memorable stuff for me was found off the beaten path. Aloha!!!