A beautiful waterfall, just outside of Hilo on the big island.
Rainbow Falls is a gorgeous and easily accessible pull-off from Highway 11. This is not really a hike - just a short walk from the parking lot to a gorgeous 80 foot waterfall (making this fun for all ages!). Hit up Cafe Pesto in Hilo for a meal after.
If you want to learn about the mythology surrounding this hike, look up the Hawaiian legend of the Goddess Hina, DemiGod Maui, and Kuna of the Mo'o (Lizard Gods). Enjoy!