As we rounded the last bit of Highway 1 before coming upon Stinson Beach, soundtracked by the clamor of a seal-pupping colony to our coastal left, we found ourselves at the foot of an ecological oasis—one that, until just last week, we had no clue existed.

Northern California is a cornucopia for all things nature, but for all its greenscaped grandeur, it seems pockets of publicly accessible woodlands commonly go unnoticed. There's no telling how many times we've all driven past the gloriously secret Martin Griffin Preserve.

"We've had people pull in here on their way to Stinson Beach asking for directions," said Claire Seda, the preserve's weekend program coordinator and our guide for the afternoon, who was crowned by a wide-brimmed sun hat and armed with enough ecological know-how to answer our most pressing natural conundrums. And boy was she eager to talk about the 1,000-acre preserve's unsung serenity. "We're always like, 'No, stay here and hike! It's way less crowded, and there's free parking.'"

Latticed by miles of clear-cut, at-times-steep trails that ebb and flow between evergreen forests and coastal scrublands, Martin Griffin Preserve—part of Audubon Canyon Ranch (ACR)—is the West Marin legacy of the ecologist of the same name, who was committed to safeguarding the local flora and fauna. Griffin, a now-retired physician and the founder of ACR, essentially defeated the condo development that was slated for the area in the early 1960s, and Martin Griffin Preserve has been protected as a wildlife sanctuary since 1962. It is among three other preserves—Bouverie, Cyprus Grove & Tomales Bay, and Modini Mayacamas—that make up ACR's land trust efforts in Northern California.

As Seda and I overlooked the nearby Bolinas Lagoon, shouldered by evergreen foothills the color of ripened avocado flesh, it couldn't be more clear: Griffin's biodiverse safekeepings are still fully intact, evident in the avian fauna regularly on display.

"People have seen osprey and even bald eagles swoop down and spear fish," she told us, as we combed the lagoon with a stationary telescope, explaining that the lagoon attracts more than 60 species of waterbirds and shorebirds—from sandpipers to pelicans—as well as some resident harbor seals. "A volunteer once, and I kid you not, found the tail of a leopard shark near where you're standing right now."

For the next hour or so, we continued exploring the various hike-able nooks and crannies that branch off from the preserve's repurposed housing units that now serve as space for on-site environmental surveys and classrooms for youth-centered programs. Newts were seen coming up for air from beneath their freshwater lairs; introductions to zoological studies currently being done by the ACR were made while we walked beneath redwood groves; and the casting of a mountain lion's paw was handed to us, along with a 25-foot rope, which just so happens to be the distance a California cougar can pounce from a standstill.

Our calves were left tender from climbing up to an elevation of 800 feet above sea level—for the sake of seeing the sweeping vistas of the Pacific Coast to our West—and then down again. (No pain, no game, no Insta-likes.)

As we parted ways with Seda, a couple toting a weighted Whole Foods bag and a crocheted blanket emerged from their Ford Fusion near the gated entrance. In that moment, we experienced the only semblance of regret since we arrived earlier in the day: Dammit, we should've packed a picnic.

// Martin Griffin Preserve is open May 5 through July 28 (10am to 4pm) each year and entry is free of charge; 4900 Shoreline Hwy 1 (Stinson Beach), egret.org.