NAVARREVISCA, Spain — Old vineyards dot the landscape surrounding this village about an hour west of Madrid. But to find the tiny, astounding Rumbo al Norte vineyard, where 70-year-old garnacha vines grow on granite and sandstone slopes threaded with quartz and strewn with gigantic boulders, you not only have to know someone, you have to earn his trust.

For as long as anybody can remember, old vineyards like this one in the foothills of the Sierra de Gredos mountains have been cherished by a dedicated few, who nurtured the vines through hot summers and cold winters. The work was exhausting, especially in the years before automation and automobiles. Simply getting to the vineyards, which can approach 4,000 feet above sea level, was an arduous project. Even today, they are tended almost entirely by hand.

The reward? For decades, the garnacha, as grenache is known in Spanish, went to the local cooperative, which made bulk wines that ended up in anonymous blends. Many growers lost money on their vines. But their attachment to the land was deep, transcending economics.

Beyond the elderly caretakers, whose children were seldom interested in carrying on their stewardship, not many valued these old vineyards. Twenty years ago, the few commercial wineries in the area were planting cabernet sauvignon and merlot on the flatlands in an effort to appeal to international markets.