Rugged, remote Howell Mountain has become Napa's most coveted wine appellation, producing some remarkably intense reds that can age for 20, 30, even 50 years.

When the little plane finally rattles off the runway, I'm glad to be aloft. I figure it's the only way I'm going to make sense of the tangled mass that is Napa's Howell Mountain. From the ground, it's too disorienting; the top of this mountain provides no vistas from which to look out over the whole. Randy Dunn, no less, is flying the plane. A 23-year veteran of the place, Dunn is one of the main reasons I'm here, as it is his eponymous Cabernet Sauvignon that put the name Howell Mountain into the vocabulary of wine connoisseurs the world over. "I knew this was where I wanted to be," Dunn says. "I liked the fact that it wasn't necessarily going to be easy to make wine." It may not be easy-but the results, for Dunn and others, have been nothing short of extraordinary.

Hundreds of feet below us, small parcels of neatly contoured vineyards sit placidly amid the uncontrolled furls of dense Northern California forest. With very few exceptions, Howell Mountain is red wine country, specifically Cabernet Sauvignon and Zinfandel. "There's my place; there's Duckhorn's vineyard," Dunn says. "Just up the road you can see the vineyards of Turley and Craig." He points out Beringer's Bancroft Vineyard, the Beatty Ranch, La Jota--a roster of names that reads like a directory of Napa's most famously collectible wines. Also some of its biggest. I remember being awed at the power of a 1987 Dunn Cabernet that last year, at age 13, was still too young to drink. I've been similarly struck by the concentrated La Jota Cabs and Turley Black Sears Zins I've had and wondered: What is it about Howell Mountain? How do these wines get so intense? That, I realized, I wouldn't understand from the air. I had to get back to the dirt.

Situated in the northeast corner of the Napa Valley, Howell Mountain rises steeply near the town of St. Helena. Though it's part of Napa, Howell Mountain is another world altogether. Unlike most Napa regions, it's covered not with tony restaurants and shiny wineries but with forest. The predominant group of settlers weren't winemakers but Seventh-Day Adventists, who are still the majority landowners. Ironically, although they are living on some of the best vineyard land in the country, Seventh-Day Adventists forbid their adherents to consume alcohol.

I clamber among the trees, my hiking boots red from the volcanic soil. There is still plenty of forest that belongs to the massive boulders, Douglas firs and ponderosa pines. Bears are regularly sighted. It's so peaceful that I find myself muttering, "I can't believe this is Napa Valley." While the tangled forests often give way to gorgeous, curving vineyards, it is a rugged land.

Robert Craig knows this quite well. Craig, who has been making a Howell Mountain Cab since 1993 at Robert Craig Wine Cellars, recently broke ground for a winery at the broad top of the mountain. Near the construction site, we pass two towering piles of rocks. "Pulled all those out of the ground just a few feet from the surface," Craig says, suggesting just how tough this land is on the grapes. Craig's winemaker, Rudy Zuidema, adds, "And 36 inches down, it becomes solid rock."

The red-colored soil with its high metal content is also deficient in nutrients. Winemakers augment it just so the vines can get by. "We try all sorts of different things," Zuidema says. "I laugh when I hear myself on the phone asking somebody their price by the ton for worm shit."

The thin soil, though, plays a large role in giving Howell Mountain grapes their celebrated intensity: It keeps yields small. "When our friends down in the valley complain about the work involved in keeping the yields down," Mike Beatty says, "we tell them, 'Grow grapes up here.'" Beatty owns the Beatty Ranch, one of the famous vineyards of Howell Mountain. He's been growing grapes since the 1970s and was a member of the small group who successfully petitioned for the creation of the Howell Mountain appellation in 1984. Mountain yields range from two to four tons of grapes per acre--compared with those of the valley floor, which can range from five to seven. Mountain grapes are also smaller, with thicker skins. They produce less juice, but it's more concentrated and tannic.

The soil imparts something else to the wine, much of the identifiable character that winemakers call terroir. "There's great terroir here," says Ted Lemon, the winemaker for Howell Mountain Vineyards, the winery formed by Mike Beatty and the owners of the Black Sears vineyard, Joyce Black Sears and Jerre Sears. Lemon achieved fame in 1982 as the first American to serve as a winemaker in Burgundy. His enthusiasm for the soil is a reflection of the Burgundian belief that wines should bear the imprint of the place where the grapes are grown. In the case of Howell Mountain Vineyards, that's two of the mountain's most famous vineyards--Beatty Ranch and Black Sears. Fruit from these vineyards also goes into some of Napa's best bottlings from wineries like Ridge, Turley and Cakebread. Lemon loves the wines these vineyards produce: "They're rough-and-tumble, rocky and earthy."

Howell Mountain stays warmer at night than the valley floor and 10 to 15 degrees cooler during the day. Thus the grapes bask in long, long hours of sunshine without the high temperatures that create baked, raisiny flavors. And flavor is key. "Mountain fruit has an intensity that's more than just color and tannin," says Beringer winemaker Ed Sbragia. "It's a giant mouthful of flavor." Sbragia is a master of mining flavor with his Howell Mountain Merlots, Cabernet Sauvignons and Cabernet Francs; they're among the appellation's most sumptuous and elegant wines.

Randy Dunn, on the other hand, makes thick-skinned, powerful wine. "I don't want to make wines that are smooth and ready to drink," he tells me. "I want to make wines that last a long time." Robert Craig, meanwhile, produces wines he hopes will be drinkable upon release. He and Rudy Zuidema work hard to prevent the tannins from dominating the wine. Craig says, "If you make a wine that takes 15 years to be drinkable, it's almost like sending your kid to boarding school."

Soon there will be even more wines from Howell Mountain. New wineries are moving in, jockeying for precious permits to clear forest and plant vines in the legendary soil. Howell Mountain is suddenly the place to be. Randy Dunn, for one, is upset by this trend, feeling the loss of Howell Mountain's unique reclusiveness, not to mention trees and animal life. But it's not hard to understand why others are eager to enjoy what Dunn has enjoyed for the past 23 years.

Outpost winery is one promising newcomer. Juli and Terry Pringle, from Southern California, founded Outpost in 1998 on the old Zinfandel vineyards of the Lamborn Family. The Pringles' first release was a 1998 Zinfandel, delicious and concentrated, brimming with fruit.

But the talk of Howell Mountain is O'Shaughnessy Vineyards, which will release its first wine in 2003. Founded by Betty O'Shaughnessy and her daughters Shannon and Kelly, three former Minnesota farm girls, theirs is an ambitious project: conjuring 22 acres of vines out of a large parcel of overgrown, steeply-graded forest. A winery is in the works, and an immense cave has already been bored out of the rock. It was the promise of quality that brought the O'Shaughnessys to Howell Mountain. "The greatest Cabernet Sauvignons in Napa are probably being produced on mountainsides," Betty says. "Although it took us three or four years to find a piece of land we really liked, when we got up here and looked around, we said, 'We've got to be able to produce some great Cabernets.'"

They probably will be able to produce some great Cabernets. Most everyone does on Howell Mountain.

Jordan Mackay is a freelance writer living in San Francisco.