Rainbow Falls sits just 2 km from downtown Hilo and is one of the most accessible dramatic waterfalls in Hawaii. The Wailuku River drops 24 metres into a wide pool that was formed by an ancient lava tube. On sunny mornings — which in Hilo means most mornings, even given the frequent rain — the mist from the falls creates brilliant rainbows in the light, sometimes multiple simultaneously. This is the best morning stop in Hilo, ideally before 10am when the sun is at the right angle.
The viewing platform is at the top of the falls, looking down rather than across, which gives a sense of the scale of the drop. Below the falls, the river continues through a deep basalt gorge. There is a short trail upriver from the main viewpoint to the "boiling pots" — a series of lava rock pools connected by underground channels where the river churns and froths. The short upper trail through the jungle above the falls passes beneath large old banyan trees. No fee, always open.