Rocaterrania is a most unlikely sovereignty. Sandwiched between New York state and Canada, it was settled primarily by Eastern Europeans who clung to old-world habits and couldn’t assimilate to American-style democracy.

Their descendants speak Rocaterranski, a syncretic hodgepodge of German, Spanish, Yiddish and the Slavonic languages, and their dress is a bizarre amalgam of 1950s Boy Scout uniforms, European military garb and traditional Hasidic hats and overcoats. Despite its proximity to the population centers of Canada and the northeastern United States, the tiny country has so far managed to retain its unique character; its borders are sealed, and in any case the inward-facing locals prefer not to stray from their beloved homeland.

If you’ve never heard of Rocaterrania, that’s because it exists only in the mind of Raleigh’s Renaldo Kuhler, a defiantly eccentric 77-year-old illustrator. It would likely have remained hidden from the world, possibly forever, if not for the curiosity of Greensboro filmmaker Brett Ingram, whose lush, penetrating feature-length portrait, Rocaterrania, illuminates the man and his work.

At more than 6 feet tall, sporting a shaggy white beard and unfashionable yet remarkably stylish clothing custom-tailored to his own design, Kuhler’s been a conspicuous presence in Raleigh since he arrived nearly 40 years ago. And while he’s delighted with the attention he’s received as a result of the film”My father always told me, ‘Son, I hope you realize the value of publicity,’” he says with a grinfor the record, it’s not his first choice for public recognition.

Lest anyone get the wrong idea about Kuhler, a man who’s produced an amazingly detailed record of a country that never existed, his feet are planted firmly in the real world. Recently retired, he spent most of his working life at the North Carolina Museum of Natural Sciences, making painstaking portraits of various animal species. “I would prefer to be known more for my scientific drawings than my imaginary country,” he says, “but I don’t have any objection. Either way is fine.”

While Kuhler’s scientific work is impressive, it’s no surprise that he’s finally getting more acclaim for the dazzling realm he conjured up in his off hours. Save for Ingram, none of his coworkers knew of his ever-evolving, lifelong creative project, brought to life in hundreds of vivid, intricate drawings and journals.

Kuhler’s detailed inventiveness knew no bounds. He dreamed up a bright, sparkling metropolis, Ciudad Eldorado, and drew everything from its magisterial, reconstructed opera house to its “prettied-up” sewage treatment plant. He takes great pride in the fact that his technique is largely self-taught; he briefly attended art school in his youth, but says “it was a disaster for me” and claims he learned more about drawing “by talking to an art teacher in a barroom.”

In 1997, Ingram, then living in Raleigh, got a job at the Museum of Natural Sciences’ media center and couldn’t help inquiring after the odd drawings on the walls of his Kuhler’s cramped office, depicting lanky, androgynous figures in skintight athletic wear from an indeterminate era.

“The first time I went in his office I saw them and I said, ‘What are those?’ And he said, ‘Oh, this is just a personal art project,’ and he passed it off. And the next time I saw him and asked about it again, he said, ‘Oh, you know, it’s just some imaginary characters I drew.’ He kind of had a defense up. So I didn’t ask him about them anymore for quite a while. But gradually he just started volunteering stuff.”

Ingram’s work betrays his own idée fixe, a fascination with lone-wolf creative visionaries. His first feature, Monster Road, about the reclusive clay animator Bruce Bickford, won wide acclaim at film festivals, including the Best Documentary award at Slamdance in 2004. In 2007 he won a Guggenheim Fellowship, which helped provide funding to finish the film he’d begun 10 years earlier about Kuhler.

As a subject, Kuhler provides a greater challenge than Bickford; the pain he experienced in his younger years, from disapproving parents and from schoolmates who mercilessly mocked his idiosyncracies, caused this sensitive, gentle man to keep the world at arm’s length. Though he’s quite open and honest when discussing his past, he’s fond of declaiming, and Ingram has to mine his gruff cadences for the nuggets of emotional piquancy that reveal his soul.

“Outsider” artists are a natural subject for documentary: Recent films like In the Realms of the Unreal, about Henry Darger, and The Devil and Daniel Johnston speak to a common attraction to talented misfits. In the hands of a lesser filmmaker, a study of Kuhler might have focused too intently on his many quirks and foibles, for comic or bathetic effect. But Ingram’s unwavering respect for Kuhler shows; he neither lionizes nor patronizes him, but rather gives him the opportunity to speak for himself.

Rocaterrania will screen at the Museum of Natural Sciences at 7 p.m. Saturday, Aug. 15. Doors open at 6, and members of Shark Quest, the Triangle-area band that scored the film, will play a short set at 6:30. Tickets are free. For more information, visit naturalsciences.org. It will also screen Tuesday, Aug. 25, at 7:30 p.m. at the Fearrington Village Barn in Pittsboro, as part of ChathamArts’ 100 Mile Sustainable Cinema Series. Tickets are $5; visit chathamarts.org.