Rainbow (Waiānuenue) Falls is a waterfall located in Hilo, Hawaii. It is 80 ft (24 m) tall and almost 100 ft (30 m) in diameter. The falls are part of the Hawai'i State Parks. There is no fee to see the falls.
Getting to Rainbow Falls from downtown Hilo is simple, but please take note that the directions in Google maps under the colloquial name are incorrect. Be certain to avoid the rough backroads that lack park access by following GPS directions to "Wailuku River State Park" (or continue reading). There are brown Waiānuenue signs posted to help once you are on the right track.
Directions: Follow Waiānuenue Avenue uphill past the Hilo Public Library. Keep going past Union Elementary School and continue past the middle school. Bear right at the baseball diamond; the left fork turns into Saddle Road. Turn right at the brown and yellow "Wailuku River State Park" sign. The parking lot can accommodate tour buses. If your legs are strong and accustomed to hills, it is possible to walk here from downtown Hilo. Bouldering is possible at the top of the falls if you wear decent shoes.
At Rainbow (Waiānuenue) Falls, the Wailuku River rushes into a large pool below. The gorge is blanketed by lush, dense tropical foliage and the turquoise colored pool is bordered by beautiful wild ginger. Monstera is also in abundance. The falls are accessible via Wailuku River State Park, Waiānuenue Avenue, coordinates 19 ° 43'9 "N 155 ° 6'34" W, and are best seen from the park's viewing platform.
Known in the Hawaiian language as Waiānuenue (literally "rainbow water"),  the falls flows over a natural lava cave, the mythological home to Hina, an ancient Hawaiian goddess. 
Rainbow Falls derives its name from the fact that, on sunny mornings around 10AM, rainbows can be seen in the mist thrown up by the waterfall. Timing this is quite a feat in Hilo! Sun is scarce, so you'll want to plan for a day with a clear morning, or wait until clouds pass. It is also best to come the day after a heavy rain storm so that the falls are running strong.
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