Esteemed critic Robert M. Parker, Jr., believes the Paso Robles area of the Central Coast shows some of the greatest potential in all of California. Here, he reports on the wineries that astonish him.

Back in 1990, there were fewer than 20 wineries in and around Paso Robles, a farming community midway between San Francisco and Los Angeles. Most of the wines produced there were rustic, highly tannic and alcoholic, with little charm or finesse. Today there are more than 170 wineries in Paso Robles, and the area is going through a metamorphosis. There are now a half-dozen or so properties producing wines that are revelations of elegance, finesse, complexity and flavor concentration. In fact, each year I spend around 10 days there tasting, and each year the quality improves. Major progress has largely come not from makers of Chardonnay, Pinot Noir, Cabernet Sauvignon or Merlot, but from a group of producers often referred to as the Rhône Rangers, specializing in grape varietals of the Rhône Valley of France.

The greatest headway has been made west of Highway 101, where most of the top vineyards are located. These are hillside vineyards planted in limestone soils of various elevations, but almost all are within 10 to 15 miles of the Pacific Ocean. These limestone soils, prevalent in many of France's finest vineyards, seem to encourage wines of great intensity as well as elegance.

Paso Robles remains a work in progress, but I believe the region already shows some of the most striking potential in all of California. The following are the six leading Paso pioneers.

Alban Vineyards

Alban Vineyards is an educational center and a virtual mecca for young winemakers aspiring to make great Syrah, Grenache, Roussanne and Viognier.

John and Lorraine Alban are unquestionably the leading Central Coast pioneers of wines made from Rhône Valley varietals, and their winery is an educational center and a virtual mecca for young winemakers aspiring to make great Syrah, Grenache, Roussanne, Viognier and Mourvèdre. John Alban began planting his estate vineyards in 1990 with what were then regarded as unknown and little-respected varietals. He has had a string of successful vintages recently, starting in 2000. Of particular note are his three superconcentrated, rich and potentially ageworthy Syrahs, including the Lorraine Vineyard bottling, named for his wife, and the Reva Vineyard Syrah, named for his mother. Seymour's Vineyard Syrah, named for his father, is Alban's flagship wine and one of California's two or three most profound Syrahs.

Alban makes a few other wines, too, including Pandora, a blend of Grenache and Syrah, which may be his most creative wine, as well as some of the best Grenaches in California, in quantities so small they're almost fiscally irresponsible. Alban wines generally cost between $24 and $45 for whites and $75 to $150 for reds, and they tend to sell out very quickly.

L'Aventure Winery

Winemaker Stephan Asseo has become a superstar, producing remarkable Cabernet Sauvignon.

Former St-émilion resident and winemaker Stephan Asseo gave up Bordeaux and moved to the hillsides outside of Paso Robles. And in just a few years, he has become a superstar, producing remarkable Cabernet Sauvignon that seems to have more in common with a great vintage of Mouton Rothschild from Pauillac than any other Cabernet I have tasted from California. This is the single best Paso Robles Cabernet and competes with the best Napa Valley Cabernets. Asseo also produces an intriguing Grenache-Syrah-Mourvèdre blend, Côte-à-Côte, that's a dead ringer for a top-notch Southern Rhône wine. Prices are relatively steep, generally running between $45 and $80 a bottle.

Linne Calodo

Linne Calodo is a name to take seriously and a reference point for all that can be achieved in the region of Paso Robles today.

Although only in his mid-thirties, Linne Calodo proprietor Matt Trevisan is already one of Paso Robles's most accomplished producers. Trevisan has worked with many of the better producers in the region, notably Justin Smith at Saxum Vineyards. Today he makes blends that are some of Paso Robles's most compelling wines.

Trevisan's white wine, the Contrarian, is a brilliant combination of Roussanne and Viognier that's a California version of a famous white Hermitage from France; his reds—which all spend time in old-oak barrels—are always interesting. Trevisan hit home runs in 2003, 2004 and 2005 with these wines. They were also stellar vintages for other Linne Calodo wines, such as the Slacker, a Syrah-dominant wine; Rising Tides, a Syrah, Grenache and Mourvèdre blend; and Sticks and Stones, a Grenache-dominant wine. But Trevisan's biggest, richest wine is the Syrah-dominated Nemesis, a blackberry liqueur–like bottling with enticing aromas of acacia flowers.

Trevisan is one of the few Paso Robles producers to recognize the potential of the region's old-vine Zinfandel, which he blends with Syrah and Mour­vèdre and labels with fanciful names such as Problem Child, the Outsider and Cherry Red. Any one of these wines will make the taster a believer not only in Zinfandel, but also in the idea that it is at its best when blended with some Mourvèdre and Syrah, which give it a nobility and complexity that the grape doesn't exhibit in a 100 percent varietal wine.

From such intriguing Zin blends to some impressive Syrah- and Grenache-dominant wines, Linne Calodo is a name to take seriously and a reference point for all that can be achieved in Paso Robles.

Saxum Vineyards

If California ever developed a vineyard rating system, Saxum's James Berry Vineyard would be classified as one of the best.

Saxum is one of the finest wineries in California, and with a total production of only about 3,000 cases a year, its wines are some of the hardest to find. Proprietor Justin Smith works with fruit from pure old-limestone vineyards that are truly of grand cru quality. In fact, if California ever developed a vineyard rating system, certainly Saxum's famed James Berry Vineyard would be classified as one of the best. Smith and his wife have recently increased their production, so perhaps their wines, all blends of Syrah, Grenache and Mourvèdre, will be a little easier to find. They're now producing other Rhône varietal blends from two other vineyards, as well: Heart Stone and Booker. All three are wines of extraordinary richness made by a truly visionary young talent who represents the very best of Paso Robles today.

Villa Creek Cellars

Villa Creek's proprietors, Cris and JoAnn Cherry, consistently produce lovely wines filled with character and personality.

Villa creek is one of my favorite wineries in Paso Robles. Proprietors Cris and JoAnn Cherry consistently produce lovely wines filled with character and personality. Moreover, the Cherrys, who maintain a restaurant nearby as well, are notable for their very fair prices, mostly between $12 and $45 a bottle. Perhaps this is because they are also in the restaurant business and understand that wine is meant to be enjoyed with a meal.

Wine drinkers should look for the Villa Creek Garnacha (Grenache) made from the Denner Vineyard, located across the street from Saxum Vineyards, as well as the Avenger, a blend of two-thirds Syrah (with the remainder Mourvèdre and Grenache) that is always complex, aromatic, rich and mouth-filling. Other recommended wines include Mas de Maha, made from a blend of Tempranillo and Rhône varietals such as Grenache and Mourvèdre, as well as High Road, a terrific wine that's predominantly Syrah and Grenache (with the remainder Mourvèdre). Also of note is the Villa Creek Willow Creek Cuvée, perhaps their most sensual and seductive wine, made from roughly two-thirds Grenache (and the rest equal parts Syrah and Mourvèdre). And last not but least is a lovely rosé, called simply Pink, that's available only at the Villa Creek restaurant and costs less than $20.

Tablas Creek Vineyard

The estate has increased quality to a point where recent vintages have been among the most interesting in the state.

It is difficult to overestimate the impact Tablas Creek has had on Rhône varietals in Paso Robles. There is its storied past: The winery was created as a joint venture between the hallowed Châteauneuf-du-Pape estate Château de Beaucastel and Château de Beaucastel's longtime importer Robert Haas of Alabama-based Vineyard Brands.

Although the winery started off a bit shakily—the early releases were of uneven quality—through hard work and rigorous attention to detail, the estate has increased quality to a point where recent vintages have been among the most interesting wines made in California. In fact, there has been a succession of very strong vintages for the winery in the past six years, starting with 2000.

Tablas Creek Vineyard produces both reds and whites, ranging from simple table wines to complex, ageworthy bottlings. The basic Tablas Creek white is a simple, food-friendly blend of Viognier, Roussanne, Marsanne and Grenache Blanc called Côtes de Tablas Blanc. It's an unoaked wine marked by generous quantities of exotic fruits. A much more complex white, Esprit de Beaucastel Blanc (an homage to the great white Beaucastel) is made with a higher percentage of Roussanne, with smaller components of Grenache Blanc and Picpoul Blanc. This is a powerful, full-bodied wine with an extraordinary nose of rose petals, honeysuckle, quince, licorice and white currants. Of course, red wine remains Tablas Creek's focus, and they make quite a few, including a California take on Côtes-du-Rhône called Côtes de Tablas. Marked by copious notes of herbs and licorice as well as cherries, it is an easy-drinking red that's usually a blend of mostly Grenache with a little Syrah, Mourvèdre and Counoise, a little-known Rhône grape.

The Tablas Creek Vineyard Esprit de Beaucastel is the winery's more serious, full-bodied red. Massive and ageworthy, it's a blend of 50 percent Mourvèdre, with at least a quarter Syrah. A deep ruby-purple wine with gorgeous aromatics of blackberries, saddle leather and roasted meats, it's easily capable of lasting 10 years or more.

The most limited cuvée made at Tablas Creek is Pan­oplie, which may well be the best Mourvèdre-based wine produced in California. An inky blue, almost purple wine with an expressive nose of black truffles, blackberry and melted licorice, it's powerful and extremely full-bodied.