No gate blocks access to the Niebaum-Coppola estate in Rutherford, in California's Napa Valley, but a sign next to the driveway does advise passers-by that the house is a private residence. A white Victorian with a wraparound porch and lots of wicker furniture, it stands on the far side of a field where sleek horses gambol. The house is shaded by a 300-year-old oak, which not long ago dropped a limb on a parked Rolls-Royce. Set discreetly to one side is a swimming pool, bright in the California sun, the only recent addition.

The estate's owners, Eleanor and Francis Coppola, live here with their two children, Sofia and Roman. They bought the place in 1975 -- reportedly for $2 million, which raised some eyebrows among the natives. The 1,500- acre plot runs to the top of a ridge behind the house, and includes some of the best vineyard land in the county, as well as some of the most beautiful. Napa traditionalists wondered what would become of the place, and what sort of wine a film director might make.

The estate was founded a century ago by Capt. Gustav Ferdinand Niebaum, who sank some proceeds from his Alaskan fur trade into a young vineyard called Inglenook and had the house built for himself and his wife. Niebaum planted vines he had imported from Europe, and his wines soon established high standards of excellence -- a tradition that has survived him.

Inglenook was closed during Prohibition. It was reopened after Repeal and run by a relative of the Niebaums, John Daniel Jr. Daniel, who also made fine wine, initiated varietal names on his labels -- such as cabernet sauvignon and pinot noir -- instead of generic names. In 1964, Daniel sold Inglenook to United Vintners but kept the house and some of the best vineyards for himself. Daniel died in 1970, and Coppola had the good sense to buy the property a few years later.

His neighbors at Inglenook -- now part of the Heublein-R.J. Reynolds group -- had also wanted the property, and for a time there was some bad blood between Coppola and the conglomerate. Meanwhile, the film director was having wine made in the old winery from his high-quality vines.

In 1978, Coppola produced a commercial red of considerable depth and complexity; he named it Rubicon. Some of those who tasted it didn't know what to make of its power and spiciness, but most people were impressed. Unfiltered and unfined (fining is a final cleaning process that removes suspended solids), Rubicon was about 62 percent cabernet sauvignon and 38 percent cabernet franc -- an unusual blend for Napa -- and threw a huge sediment.

A similar style of Rubicon was made in '79 and '80. The wine was still impressive, but critics questioned its balance. Then, after a brief hiatus, the style began to change. Coppola hired a new winemaker, Steve Beresini, from Phelps Vineyards, and in 1983 enlisted the services of Andre' Tchelistcheff, the consultant and grand old man of Napa wine-making. Tchelistcheff advised Coppola to reduce the percentage of cabernet franc, and to filter and fine Rubicon to make it a brighter, more stable wine.

"It's a cheap insurance policy," says Beresini of the new wine-making regimen, drawing a glass of deep ruby wine from a barrel and holding it up to the light. Clean wine is not as apt to go "off" once transported and is highly prized nowadays by consumers, who don't know what to make of sediment.

Filtering and fining often strip red wine of character, but that is not the case with Rubicon. It has been tamed a bit, but the effect on the palate is still profound. The '85, for instance, has a big cherryish nose and plenty of spiciness from the cabernet franc. The '86 is even bigger, with a long, complex finish.

The components of Rubicon have also been altered to include some merlot. Beresini blends immediately after fermentation and then ages the wine in French oak barrels for about two years. Unfortunately, Rubicon can be hard to come by. Only 4,000 cases are now produced each year -- approximately half of the planned eventual production. A bottle costs about $25.

Of course, the old Niebaum vineyards are the real heroes of this success, providing fruit of great concentration and flavor. Inglenook, whose new management has mended fences with Coppola, gladly buys the grapes he doesn't need. Some Niebaum-Coppola cabernet franc went into Inglenook's stunning red wine, Reunion, just released.

Coppola's vineyard manager, Rafael Rodriguez, looks after the 83 acres of grapes -- the same responsibility he first undertook for Inglenook in 1952. "The Coppolas," Rodriguez says, driving his pickup with care among vines he knows individually, "want to keep the property like it used to be. It's the answer to a prayer."

Last fall, Rubicon shared the cellar with racks of tapes used in mixing the sound for Coppola's latest film, "Gardens of Stone." The top floor of the winery is a full-fledged recording studio, with a big screen and sumptuous couches for viewing Coppola's handiwork. Wine and movies seem simpatico.

Rodriguez, at Coppola's bidding, will soon plant the field where the horses play; the vineyard will be named for Coppola's son, Gian Carlo, who was killed in a boating accident last year. It will be 70 percent in cabernet sauvignon, 15 percent in cabernet franc, 15 percent in merlot.

"The Rubicon blend," he adds. ::