With its discreet trailhead, you might not really be sure you’re in the right place at first. Ka’au Crater Trail begins at the end of Wai'oma'o Street on the Maunalani Heights-side of upper Palolo Valley. It’s an unmaintained hiking trail that mostly follows an above-ground city water pipe system until you pass the first waterfall and begin a steep 2,020 foot climb up muddy slopes.
Hawaiian myth places the crater in the center of a failed attempt by the god Maui to consolidate the islands of Oahu and Kauai into one unified land mass; rather than succeeding, his magic line snapped, his hook slung back deep into the spine of the Koolaus ridge, creating this marshy scar. Geologically, Ka'au Crater is just a tuff cone, the result of a violent surge of molten rock from deep within the Earth, similar in formation to the more well-known Diamond and Koko head craters on Oahu.
Now with all that violent imagery in mind--
WARNING: this is a very difficult trail. It is unmaintained, mostly vertical and extremely slippery. Do not do after a heavy rain and take plenty of water. You will cross through creeks and scramble up waterfalls. In some places you'll need to downclimb in an almost rappel-like fashion on knotted ropes. These ropes are placed by locals and none of them are necessarily checked or maintained. Be cautious and alert at all times!
WHAT TO BRING:
Keep in mind you'll be sweaty, hot, hiking mostly vertically and trekking through creeks, mud-holes and waterfalls.
HOW TO GET THERE:
Put the Palolo Zen Center into your GPS and park along the road outside of their marked tow zone. If you get there early (which to start this 6-8 hour hike, arrive around 9 or 10 a.m.) parking shouldn’t be a problem.
Walk up the road until you see a row of mailboxes on the left side; just behind them is a yellow sign reading “Ka’au Crater Trail is an unmaintained trail, enter at your own risk!” Slide down into the jungle over some roots and boulders to start the trail.
In general, the Ka’au Trail is easy to keep track of. There are no real satellite trails, so just stay on the most “worn” path and you’ll always be heading in the right direction. Early on, you will find a junction where you can choose two ways of hiking the rim:
For those who want to use the easiest (and safest) ascent, continue left up a forested switchback area to the top of the crater rim—be sure to turn around at some point and come back this way as well. NOTE: you will not see the waterfalls on this portion of the hike. For the best of both, the first and most impressive waterfall is well worth hiking to separately, then backtracking to the junction to ascend the crater.
For those who want more of an adventure and a challenge, continue right, hike to the first waterfall and continue straight up through two more steep sections of waterfalls and muddy slopes.
For the latter, you can hike the loop in either direction, but I recommend doing it this way; it’s safer to hike up the waterfall sections rather than down, especially considering the fatigue you’ll feel in the second half of the hike.
Once you ascend the top, take a moment to sit down, drink some water and be present in your surroundings! You’ve made it to one of the highest points in Oahu (2,020ft/616m above sea level) and have an unobstructed, 360 degree view of the island. It’s not over yet though, the hike down will require a lot of scooting and shuffling.
Many areas force you to squat down, hands to soil, and slide. Keep your center of gravity low in these spots; once you start traversing the easternmost ridge you are one wrong step away on either side from falling off the face of a steep cliff. That'd be a really awful way to end the hike.
I want to reiterate again, DO NOT do this hike after a heavy rain and proceed with caution if going alone. Tell someone where you’ll be and when to expect you back. There have been a couple tragic deaths on this trail in recent years so use common sense and always be aware of your surroundings. Listen to your body, take as many breaks as you need, and please practice Leave No Trace ethics!
Be safe, take pictures and enjoy this beautiful land.