Here’s an informative article on Rainbow Falls by Katie Young Yamanaka for Hawaii.com.
Rainbow Falls is a favorite stop on the Big Island Circle Tour.
One of the most easily accessible waterfalls on the Big Island, Rainbow Falls is just a quick five-minute drive from downtown Hilo.
On sunny days, rainbows appear in the mist of the 80-foot falls, making for some pretty magical views. The broad waterfall — nearly 100 feet in diameter — plunges over a natural lava cave and into the river below.
When it rains, (which it often does in Hilo), the engorged Wailuku River makes the falls wider, muddier and louder. On these days, you won’t see the rainbows for which this spot is named, but the sheer volume of water and the accessibility of this spot for all ages make it a fun, quick and easy excursion.
The paved parking lot, which has a dozen car stalls and a few larger spots for tour buses, leads straight to the viewing platform where most visitors gather for the best photo ops of the falls.
If you are game to climb a couple dozen uneven rock steps (there is a metal railing on either side to help you get your grip), you will be treated to a bird’s eye view of the falls from above, including a glimpse of the less dramatic side of the Wailuku River.
The path at the top doesn’t lead very far through the forest of trees, however, and there are warnings against jumping or diving, the potential for flash flooding and not wandering off-trail because of the hazardous cliff. There may be a few souls who attempt a swim in the ponds at the top, but this is NOT advised.
The Legend of Hina
Known in the Hawaiian language as Waiānuenue — literally “rainbow water” — it is said that the Hawaiian goddess Hina, goddess of the moon, dwells in the lava cave behind the curtain of the falls.
Hina is the mother Maui, another storied demigod in Hawaiian mythology who is best known for lassoing the sun so that he could help his mother dry kapa (cloth made from tree bark).
Maui also helped save his mother from certain doom after a giant lizard named Mo‘o Kuna hurled a boulder over the cliff, blocking the entrance to Hina’s cave. Cold water began to rush in as Hina slept. Maui used his club to split the giant rock in two, freeing his mother. The two parts of the great boulder, known as Lonoka‘eho, are now overgrown with tropical plants but remain as a reminder of Maui’s strength.