The 'Blue Hole' is at the base of Wai'ale'ale, which is just below the cliffs that one of the wettest spots on earth. Locals refer to this location as the Wailua Headwaters; it's where you see the falls coming down the wall. This page is meant to direct you to the Weir (stream diversion) where you can see into the Wai'ale'ale basin; it is not meant to guide you to hike to the Wailua Headwaters. Having done the hike to the back wall myself, I can say with some certainty that the 'Blue Hole' hike is extremely difficult and technical, and for that reason this page is not meant to direct you to the actual 'Blue Hole'. Many people have gotten disoriented attemptiong to reach the Wailua Headwaters; even locals who are familiar with Kauai have been stranded and had to spend one or more nights out in the jungle with no supplies. Moreover, rain can occur quickly and heavily in this area; if it does, the river will flash flood and if you are above 'Guardian Falls,' the way will be impassable until the water subsides. It is not uncommon for clear ankle deep water to trun into a chest high raging torrent in under an hour - you need to be aware of the signs that the environment is changing before it occurs; otehrwise it may be too late to get out before a flood. I cannot stress the importance of this enough; every year people die on Kauai in flash floods and hunders get stranded and either have to spend the night or be rescued by helicopter. A helicopter rescue in Waialeale Basin would be extremely difficult and dangerous and there is no guarantee that you would even be able to get help as cell phone receiption is spotty up in the basin.
If you want to take a good look at Waialeale, go for a moderate hike with knowedgeable local guides, and return home cozy and warm after a 1/2 day, we recommend Aloha Kauai Tours. They have been operating tours on Kauai since 1990 and have a wonderful rainforest group excursion that begins at the 'Jurassic Park Gate' and takes you to the weir.
At the end of Highway 580, Kuamo'o Road will end abruptly at the Keahua Stream crossing near Keahua Arboretum. You can park in the parking lot on your left and begin your hike (unless you have 4x4, then you can proceed at your own risk). The drive beyond the paved highway is very rough, bumpy, often muddy, and dangerous in spots (especially when crossing streams).