Imagine that you’re in an east shore valley. You come upon a tunnel that’s a mile long. From the moment you enter, you can see the light at the other end. When you emerge, you’re in the virtually inaccessible back of the north shore’s Hanalei Valley, surrounded by nearly vertical mountains, a perfect river and no people. Aside from a few hunters, almost no one on Kaua‘i had even heard of this tunnel until we revealed it. Those who had heard of it considered it one of those urban legends, a myth. Well, it’s no myth.

In the 1920s a sugar company was seriously coveting the abundant water flowing out the Hanalei River. They needed the water for their east shore sugar. So for $300,000 they cut this tunnel and diverted 28 million gallons of water a day under the mountain and into a series of ditches to quench their thirsty crops. But times change. As sugar production dwindled on the east shore, they found that they no longer needed the north shore’s water. So, years ago, they stopped diverting the water and abandoned the dam. The flume to divert the water is no longer there. They couldn’t divert water into this tunnel even if they wanted to without doing major reconstruction on the dam. But the tunnel, blasted out of solid rock, remains.

Getting there will be a sloppy affair. It involves walking 2.5 miles along a trail through muddy conditions. (It rains about 160 inches annually here, spread fairly evenly throughout the year.) The footing, terrain, overgrowth, washed-out trail sections and ferns hiding pockets of nothingness make it one of the harder 2.5 mile stretches you’ll find in Hawai‘i. Bring a low-profile pack to reduce snagging vegetation during the many incidences of ducking under brush.


Driving to the trailhead means taking a dirt road. A regular car can go part of the way, but it’s hard to say how far. There’s an old truism—What’s the difference between a 2WD rental car and a 4WD SUV? A 2WD rental car can go anywhere! Meaning, it depends on how much you’re willing to punish it. This road is sporadically improved, and it depends on your timing. But for our purposes, 4WD is the way to go here. See directions to the Jungle Hike, and stop just before the first gate. Accept from the get-go that there’s no way to keep your feet dry. Spiked tabis (described here) work best, and you might find them at Discount Variety in Koloa or Walmart. The downside is that your feet will feel a bit tender when you’re done. Long pants are also recommended. Ferns have a habit of sticking out in the trail, scratching at your legs. Jeans are ok, but they get heavy and stick to your legs, making it harder. Lighter pants are preferred. Look for delicious red thimbleberries along the way. (The redder, the better.) Bring a flashlight/headlamp (or two) for the tunnel. Also bring water and snacks.

North Shore Hawaii

A hiker marvels at the richness of Kaua‘i, which is ever-present on this trek.

The trail to the tunnel is a hunters’ trail, and it’s always muddy. The first 100 yards are very sloppy with a permanent puddle near the place where you park. Several short stretches are on uneven terrain, and caution needs to be taken. In the first 5 minutes you’ll have to cross the Wailua River twice. Usually it’s done by hopping across a couple of rocks. If it’s too deep and you aren’t comfortable, don’t go. If it’s been raining a lot, don’t go. During very heavy rains you may find that the river isn’t crossable coming back, presenting you with a dilemma. Just after the first crossing, go diagonally upstream about 150 feet and look for a trail in the bamboo thicket. (It’s not the trail going straight ahead from the river). Bamboo is the best natural material there is for walking sticks, and it’s a good idea to have one on this hike. (It makes a good spider stick in case there are webs across the trail.) Cut it so that a knuckle is near the bottom, acting as a natural stopper, preventing dirt or mud from filling the hollow tube. Shortly after the bamboo thicket the trail becomes more vague—keep an eye out for where it bears right.

The trail is intermittently “paved” with ‘ohi‘a tree logs looking like railroad ties from long ago. Avoid false trails. Remember, you’ll never go more than 15 minutes without seeing the ‘ohi‘a logs. (Hunters—and their dogs—who use the trail mostly on weekends and Mondays often put their own tags on trees, and following them might help, or they might take you off the main trail.) You’ve gone almost a mile when you see your first old, abandoned wooden power pole. Just after this you come to a flat muddy area and a trail to the left. We’ve walked through the flat part and sunk 3 feet into a bog. You’ll cross a couple of smaller streams (a foot wide) and a slightly larger stream.

After 1.5 hours or so, when the trail encounters a large stream again, it seems to end. This is where people get lost. It actually veers slightly left, away from the stream and over some rocks. Pick your way over the boulders, staying on the left side of the bank, and look for muddy stains on the rocks—they will lead you to the trail in the tall grass ahead. It crosses the stream where the stream makes a right turn. Once you cross, pick up the trail directly on the other side, and it’s not far before you walk on a skinny plank bridge over a ditch. The trail goes to the left (and uphill) to the gauging station and tunnel. You’ll notice a tunnel to the left and a little farther on, one to the right. You want the long one on the right (the left side is shorter and doesn’t lead to anything). It takes us 2–3 hours to the first tunnel, and about 45 minutes in the tunnel. You’ll gain about 600 feet with all the ups and downs.

Once in the tunnel, you’ll notice that there’s water standing in it. That’s from the small amount of water that drips from the ceiling. It’s just the right amount to keep about 4–8 inches of water fresh. The tunnel is about 6 feet wide and 7–10 feet high with an occasional need for a head duck on the straight portion. The bottom is flat and lined with small rocks, which makes for fairly straightforward walking. The tunnel reverberates with the ever-constant sound of the splashing of your feet in the ankle-high water. About 900 feet above you is the ridge that the ancient Hawaiians used to walk on to reach the summit of Wai‘ale‘ale where the remains of their altar, at one of the wettest spots on Earth, may still be found. As you approach what appears to be the end, you see an odd sight: railroad tracks in the shallow water, probably used to haul the debris out of the tunnel during construction. At the light at the not-quite-end of the tunnel, you can step outside momentarily to visit a small waterfall waiting for you. Then it’s back in the tunnel for the remaining 0.25 miles. That latter portion is partially lined with cement and shorings, requiring anyone 6 feet tall or more to duck for a bit. At the real end you need to follow the now-exposed ditch for a hundred yards or so, keeping an eye out for a faint trail on the right that goes over a ditch. It goes down for about a minute to the Hanalei River. During good weather the scenery is magnificent. The mountains tower all around you. Wai‘ale‘ale plateau is above and to your left, its side etched with waterfalls. The river, with some impossibly large boulders, makes a perfect place for lunch.

Most will be more than satisfied with this destination. But if you started early (hiking by 7 or 7:30 a.m.), there is one more challenge for the intrepid. You’ve been through a mile of tunnel already and are at the river. Directly across from the giant boulder and deep pool (you’ll see it), there’s a very faint trail on the other side of the river that leads 5–10 minutes upstream to another 0.7 mile-long tunnel. It’s more dicey.

Follow the trail across from the boulder, past a bamboo grove where your route looks more like a game trail, until it meets an old diversion dam (that looks like a waterfall, which you’ll hear). From the top of the dam look upstream, then turn to your right. You should see a vague trail going directly uphill. It will take you to a cement wall (part of the next ditch). The next tunnel entrance is over the wall to the right.

Once inside the tunnel (known to hunters as Ka‘apoko Tunnel), there’s lots of head ducking, and it has a more rickety feel. When the tunnel ends, there’s an offshoot to the left. Not far from there, you come to a low-ceiling incline with water gurgling down. Scoot up and you’ll emerge in a Shangri-la that will make you giddy with joy. A cathedral of 200-foot sheer walls is so steep they actually lean inward. Water drips from above, creating an exotic backdrop. To the left is a pounding waterfall. The setting is unbelievable and worth all the effort you went through to get here.

North Shore Kauai

Hikers entering the tunnel.

Besides enjoying the sheer beauty of the scene, look for a third tunnel across the river. There is a small stream trickling down from the entrance. The tunnel takes another 10 minutes and gives different perspective on the valley.

The trail conditions seem to get worse every year, and at the risk of sounding self-promoting, you’d do well to purchase our smartphone app to keep from veering off the trail. It’s geo-aware, and we GPSed this trail (and all Kaua‘i trails) ourselves to make sure the track is spot on.

Needless to say, you’ll have the opportunity to get big-time muddy, slip on your ‘okole, bump your head, twist your ankle, etc., on this adventure. Use your best judgment. This trail and tunnel are not maintained for this purpose, so please don’t complain to anybody if you have any problems. This is a strenuous, exciting and memorable adventure with absolutely no guarantees. That’s why it’s an adventure. This is the secret tunnel only we have revealed apart from few hunters on the North Shore Kauai.

For more info on any of the islands, download our Hawaii Revealed app.