MY FRIEND Jeremy and I are baby-stepping down a path—gingerly, oh so gingerly, because by “path,” I mean a jagged scar through a vertiginous deathscape of blackberry brambles, undoubtedly forged by a secretive and murderous cult—into a narrow ravine near the banks of the Willamette River.

“Maybe we’ll disappear down here,” Jeremy says. “Maybe we’ll be forced to live wild.”

“And the Discovery Channel will come in to find us,” I say.

Unofficially, we’ve just crossed a sharp psychic boundary, one that divides the precisely landscaped residential streets of the Overlook neighborhood from menacing botanical anarchy. Officially, we’ve entered Mock’s Crest, one of two expansive bluffs that make up the area called the Northern Willamette Escarpment, 200 acres of weedy North Portland acreage that stretch along the east side of the river from around the Fremont Bridge up to St. Johns. It’s the ridge that thrusts North Portland above the rest of the city, an amorphous green enigma rearing up above the Union Pacific rail yard and the traffic that rockets down N Greeley Avenue and N Interstate Boulevard.

I’ve wanted to explore this place for some time now. My wife and I often walk through Overlook, which isn’t far from our house off of N Mississippi Avenue. To me, Overlook has always seemed to be the perfect distillation of “Portland Nice”: It’s home to a weekly farmers market and a couple of expansive parks, and it’s just a healthy stroll away from coffee shops, restaurants, a MAX light-rail line, and other home-resale-value-enhancing amenities.

But then there’s this steep plunge into tangled quasi-wilderness to the very immediate west, which I guarantee does not receive prominent play in real estate ads. Periodic signs of human activity along the escarpment’s upper edge paint a less-than-benign picture: bushwhacked trails cutting down into darkness, littered with empty booze canisters.

We’ve crossed a psychic boundary, one that divides landscaped streets from botanical anarchy.

During my humble family excursions, I eye those trails with both fascination and leeriness. We Portlanders are justifiably proud of our trophy green spaces—the Forest Parks, the Powell Buttes, what have you—and the way they embody our city’s crunchy harmony with nature (or, at least, with nature trails). We love our urban wilds, but we prefer them well-maintained, recreationally accessible, and without that murderous-secret-cult vibe. Within the Portland family of parks, the Willamette Escarpment is the second cousin who has three teardrops tattooed under his left eye and who starts recounting Measure 11 offenses after a couple of drinks.

What could be down there, I wondered? A colony of hyper-evolved, iridescent spiders the size of Toyota Scions, communicating via telepathic vibrations? A village of neo-Druids on a prolonged bad trip that started in 1967? Anything was possible. I pictured myself in a pith helmet, machete in hand, plumbing the escarpment’s hidden depths. However, given the prevalence of alcohol-related detritus, it also seemed plausible that any humans I encountered might not appreciate a slumming middle-class idiot wandering through an area that any other moron would recognize as obviously Off-Limits. So I recruited Jeremy, a highly capable (he can build things and so forth) and physically formidable (he thrashes me in racquetball) pal. Should any denizens cut up rough, Jeremy could protect me, I wagered. Or, at least, I could bargain his life for mine. And so we locked our bikes to a streetlight pole in Overlook and plunged in.

“Dude,” Jeremy said, kicking at the underbrush. “Don’t disturb that malt liquor can. It’s an important part of our heritage.” True enough. Before the perfidious hand of the White Man made its play, oak and madrona trees shaded native grasslands along the bluffs above the Willamette. Now, beside discarded Colt .45 rounds, invasive species like Himalayan blackberry and Scotch broom run amok. On occasion, the plants have ignited into raging wildfires—a boon to alarmist local TV newspeople, but for bluff-side property owners, not so much. The degree to which this corrupted landscape can be enjoyed as a “natural area” depends on an individual explorer’s ability to appreciate abandoned shopping carts rusting away in the scrub. We find a particularly fine specimen about 100 yards down the path.

And yet our trail soon levels out in a little bowl carpeted with ferns and splintered branches. Dry, severed ivy vines hang from crooked maple trees and summon an image of a young, glistening Tarzan swinging his way from branch to branch, ululating with abandon. The light, filtered through the dense canopy above and limited by the claustrophobic ravine walls, takes on an oozy, surreal quality. The flora is spongy and ankle-sucking, the footing uncertain. Up ahead, we spy the outline of some man-made structures, a little lookout fashioned from plywood scraps—like a duck blind, except I’m pretty sure the architect wasn’t hunting ducks—and a rustic tree house. Jeremy clambers up the four-step ladder to a wooden platform about six feet off the ground. It’s just big enough for one small person to stretch out on.

Someone, at some time, decided this would make a secure bivouac. Not like it’s going to become a UNESCO World Heritage Site or anything, but the tree house serves as a telling cultural artifact of this landscape’s present state of feral abandonment. As it happens, that state might not prevail for long. Shiny signs along the cliff announce a government project to wipe out invasive plants and restore the escarpment to its original, oaky state. Out of curiosity, I called the project’s manager, Mark Wilson, before my trek into the urban jungle. He explained that some big, blackberry-fueled fires early in the decade unnerved city officials, so they formed an interagency task force—which, in turn, created a multiyear project funded by the Federal Emergency Management Agency (good for something!) to re-primordialize this ragged sliver of North Portland.

“There’s a lot of potential there,” Wilson said. “The oak and madrona savannah is a pretty rare habitat, and there aren’t many places in the metro area to do something on this scale.” The city’s posted signs sum up the project’s ambition by describing a “desired future condition”: a loose tree canopy that towers over native grasses and shrubs, and that someday could become the site of educational field trips for schoolchildren.

My God—it almost sounds like a nice place for a walk. Behold the Portland ethic in action: Where other cities might see a weedy bandit’s lair, we see a chance to strike a blow for ecological rectitude. As Jeremy and I head toward the white-noise roar of N Greeley Avenue, I try to imagine our current path transformed into an Eden. Of course it would be a good thing. As a right-thinking liberal, I could only applaud the enlightened city in action. (Think what a luxury it is, in human historical terms, to have a local government that worries about native plant restoration. Beats the Borgias.)

Yet after we leave the tree house and the other fortifications installed in these unwelcoming woods by parties unknown, for reasons unknown, I feel a pang of pre-emptive nostalgia for the gone-to-seed vigor of the escarpment as it is. I can think of few other places where this riotous profusion of greenery (not quite the kind most Portlanders approve of, of course) could exist just beyond the pale of settlement. In a well-ordered, progressive city, a place like the escarpment represents a messier kind of freedom—where danger intermingles with the possibility that, within a mile of my espresso bar of choice, I could choose to disappear into terra incognita, go live among the Tree-House Tribe. It also provides a healthy reminder that any city—even green-friendly, sustainability-mad Portland—exists at the edge of nature, not vice versa; there’s always an implacable wave of undergrowth waiting to take back any available space.

Beyond the broken glass, Jeremy and I discovered that the escarpment is not without beauty. We saw wildflowers. We saw a red-tailed hawk. We saw a hipster couple who’d ridden their bikes out to the cliff’s edge and brought a sleeping bag to cuddle in. We even saw a few tough old oak and madrona trees—stubborn survivors, right at home.