"Don't look down," Mark Ruffalo says. He's leading me up a rust-covered steel ladder welded to the back of an abandoned five-story coal silo, with decades of ivy growth spread over its sides, for a panoramic view of his adopted hometown of Callicoon, New York (pop. 216). It's just before dark, not the ideal time to be scaling decrepit landmarks, and we're freshly arrived from the tavern across the street: These are high-school-level high jinks and Ruffalo knows it. "What are we doing, right?" he asks, near the top of the ladder. "We've got kids."

Inside the clapboard housing atop the silo, it's dim and derelict, with a giant snarl of gears occupying most of the space. Some mangled boards are arrayed loosely around the floor, bridging at least one ferocious gap. "Step on this board," Ruffalo says. "You don't want to fall down there." When we're both on semi-stable footing, Ruffalo exhales a satisfied-sounding breath and takes in the view through a pair of windowless openings: a swath of gloamy violet sky, the moon-colored ripples on the Delaware River, the 1940s theater on Upper Main Street and the mansard-roofed Western Hotel a few doors down, the deserted sidewalks silent save for jukebox chords that come spilling out when someone steps from the tavern for a smoke. There's a rustic, timeless quality to the scene, like a Currier & Ives print updated with a few smudgy industrial details, and it clearly enthralls Ruffalo. "I thought about buying this silo for an office or something, but it was never clear who actually owns it," he explains. "Plus, it's gotta be so contaminated, right? Like a Superfund site." He takes another long look; you get the feeling that, given a chair and a tub of popcorn, Ruffalo could perch here for hours.

It would be an understatement to say that Mark Ruffalo's life has undergone some changes since 1995, when, as a fledgling 28-year-old actor, he happened upon Callicoon and with the recklessness of true love plunked down $63,000 for a one-room cabin on 27 acres. ("I owned my second home before I'd had my first apartment," he says.) There was, for starters, his breakout role in 2000's You Can Count On Me, which catapulted Ruffalo to indie-idol status; a series of powerful yet nuanced performances in Eternal Sunshine of the Spotless Mind, Zodiac, and Martin Scorsese's Shutter Island; and an Academy Award nomination for his role as the tousled, endearingly feckless sperm donor in The Kids Are All Right. His directorial debut, Sympathy for Delicious, in which he costars, hits theaters this month, and he's signed on to play the Hulk in Joss Whedon's forthcoming The Avengers, his first foray into mega-budget, summer-blockbuster fare. That's merely the professional side—the nine-to-five. In his personal life, there's been marriage, three children, a brain tumor that left his face paralyzed for much of 2002, the unsolved gunshot death of his brother in 2008, and an eco-political awakening that's recently put him at the forefront of opposition to a controversial gas-mining process known as hydraulic fracturing (earning him enough infamy that he was rumored to be on the TSA's "no fly" list). Yet Callicoon, that tiny little town with its vaguely Dr. Seuss-ian name and mellow, alt-country vibe—along with the stream-riddled woods surrounding it—has remained Ruffalo's constant: the one thing, aside from his family, that keeps him bolted to the earth despite the rocket thrust of stardom, not merely his retreat but his home ground, his fountainhead, the place he could watch for hours from the dark, rickety confines of a coal silo.

"I grew up in a classic suburban housing development, but on the edge of a forest," he says, explaining the draw. This was in Kenosha, Wisconsin, where his dad ran a painting business and his mother was a hairstylist, and Ruffalo was the oldest of four kids. Playtime was spent in that forest. "Those days in the woods were pretty magical for me as a kid. Your imagination can run completely wild, you can be whatever you want, whenever you want, and the days are just endless." For an outdoors role model, he had his grandfather, a Quebecois fur trapper who lived on the fringes of massive swampland in northern Wisconsin: "a gritty guy, living off the land," he says. "He scared the shit out of me, but I really respected and admired him. There's something heroic and interesting about that type of man." In Callicoon, Ruffalo found "the same kind of land, same kind of people, same kind of forest. I don't know why, but it just felt like home to me."

He's telling me this over drinks at Matthew's on Main, where roughly half the drinkers bellied up to the bar are wearing paint-spattered dungarees and where Ruffalo is enough of a regular that the bartender tells him his wife, Sunrise Coigney, stopped in earlier to look for him. "The Ruffalo kitchen," he jokes, ordering up some guacamole with tortilla and potato chips. Just this morning he was in Manhattan (two and a half hours to the southeast) for a last-minute refitting of his costume for The Avengers. Ruffalo as a comic-book superhero is hard to reconcile with his Agway look, his loose, unguarded demeanor, the way he's munching potato chips and engaging the waitress in parenting shoptalk. It's like one of those Russian nesting dolls, with the Hulk being played by the action-movie star being played by the art-house idol being played by this upstate guy in a blue-check plaid flannel shirt, jeans, and a tattered brown baseball cap with a salt-and-peppery scruff of beard and a tendency to ask as many questions as he answers. Though Ruffalo has owned land hereabouts for 15 years (eventually, when a family arose around him, he traded in the one-room cabin for a multi-room house on 47 hilly acres) and planted himself here whenever and however his schedule allowed, it's only since 2009 that he's been living here full-time. Before then, he felt obligated to do "the Hollywood thing," and though ostensibly referring to the house he and his wife owned in the Hollywood Hills, he's not talking just geography.