Located just a short distance from downtown Hilo on Waianuenue Avenue you'll find Wailuku River State Park which consists of 16 acres along the Wailuku River (lit. waters of destruction), the longest river in Hawaii at 18 miles in length.
The first attraction you'll come to is Rainbow Falls. This 80 foot tall waterfall drops over an ancient cave that is said to be the home of Hina, the mother of the demigod Maui. In the early morning sun, rainbows are easily seen in the mist that rises as the water hits the pool below. You can view the falls from parking lot level or climb a series of slippery steps to view the falls from above.
A couple of miles upriver you'll find a small parking lot where you can stop and view Pe'epe'e Falls and Boiling Pots. This is a particularly rough area of the river. Water falls over Pe'epe'e Falls and then enters an area of rapids known as Boiling Pots where the water rushes through old lava rocks and lava tubes and appears to bubble up or boil as it makes it way downstream. There is a trail that takes you close to the river, but it is dangerously close to the lava tubes and numerous drownings have occurred in this area.