Remember King Kamahameha? We start the Ironman in front of his, ah, hotel. But the King himself didn't stay there. He and several thousand of his people hung out in Waipio Valley. I know why and I'll give you a little taste of it here.

I first came to this island for the Ironman in 1981. I spent the first 30 years the way many triathletes spend it: I didn't come to Hawaii; I came to the Ironman. And then I left. My attitude was one reason we have an uneven relationship with those who live here. We're like guests who accept a dinner invitation only for the meal.

I've ventured out more this decade, and the more I explore the more I realized what I missed. I wrote about extra-Konacular adventures last year, when three groups of us were in the northern part of the island on the same day, each doing one thing or another. My cover shot for that article was Waipio Valley although I'd never been there.

This year I went there. I and our man Lars Finanger. This image above is of the Z Trail. We'll get to that. But first, one of the groups who explore this part of the island is the ENVE crowd, hard core cyclists whose rides intimidate me. Below they're getting ready to head from Hawi (Ironman's bike course turnaround) to Waimea, which begins with a 3,000 foot climb.

As I understand it, ENVE's Neil Shirley demolished the Strava segment for this climb, and if so then not far behind would be Jake Pantone from ENVE pictured just below, near the summit. I believe that should be Maui's 10,000 foot Haleakala volcano in the distance.

If you're ENVE and you're on this part of the island, you'll insist gravel is involved. In the pic above, this is past Hawi, perhaps out Old Kohala Mill Road. This particular ride was 78 miles with 6,100 feet of climbing.

Lars Finanger owns an agency that manages many of our key accounts at Slowtwitch, and he also puts on the Orcas Island and the Casco Bay SwimRuns. I'd talked Lars into an adventure without realizing it. I told him about Waipio Valley (above) last year and then forgot about it. But it stuck and he arrived on the Big Island ready to tackle it.

I already ran it the day before, but not all of it. In fact, not half of it. Time and leg constraints restricted me to a downhill from the Waipio Valley lookout—the official start—a valley crossing, and one uphill on the other side of the valley (you can see a little of what it looks like above). This all took me 90 minutes, what with getting lost, calculating where to negotiate a river crossing and the like.

This run is 19 miles long, with ridiculous climbing and descending. You start at the Waipio Lookout, about a thousand feet above the sea. The run down to the valley is paved, barely, is one lane, and it averages about 22 percent with pitches near or over 30 percent. It's maybe two-thirds of a mile long. My quads were toast when I got to the bottom.

Lars had a photog accompany him for part of it, Aaron Palaian, and most of what's herein is his. After descending the road it's all dirt, and the first part is running out to the ocean. You've got to cross a river and it needs to be done as it exits into the sea. Here's Lars, above, just after the crossing.

Then you enter a canopied trail (after nosing around to find it), cross the valley and ascend the other side. That's well steeper yet. Partway up that is as far as I got.

Then it's up and down, between 1,000 and 1,500 feet, and remember it's Hawaii. It's hot and humid. Lars texted me after it was over. "Insane! Ran out of water and electrolytes, cramped really badly, so resorted to these little fruits and the stream falls." Don't know what those fruits are. You can see Ghost of Lars in the stream image.

Finally you run down into another broad valley and then return. There's a Strava segment for this run, one way, it's about an hour and a half, but for most people the round trip is 4 or 5 hours from what I hear.

It's an out and back, here's Lars on another section of the Waipio Valley trail above.

On my trip out I ran into some company. There's a herd of wild horses down in this valley, most are paints like these, smaller 12 and 13 hand ponies, plenty of fresh water and whatever it is they eat. I startled the first one I came upon as he was rolling around on his back in the sand. Run right past them. They probably won't let you approach them, but they won't hurt you.

Here's Lars just after crossing the river on his return. This river is either knee or waist deep depending on the tide. I hit it at high tide. Best not try to be dainty. Just run through it, SwimRun style.

the Z Trail ends with a 1,000 foot climb up the road you ran down. I had to paperboy the darn thing even while running it. Or as close as I came to running.

Lars at the finish above and that 25 degree pitch sign is a lie. That's closer to an average for that nasty thing. I did note there's even a Strava segment for the climb up it on a bike. Look it up. Some pretty august names on that list you'll recognize.

I've got next year's adventure already planned out. It's going to take some politicking. Where I want to go is big medicine, I suspect, where even the locals are rarely welcome. I'm not going to fence hop. If I can get this done I'll have some wowza pics for you next year.

ENVE PHOTOS: Mike Swim
Lars PHOTOS: Aaron Palaian