I thought I knew everything about Port wines until I visited the rugged Douro River Valley in northern Portugal for the first timeand enjoyed the beauties of aged Tawny Ports, delicate and fragile fortified wines that have been made in the region for more than 300 years.
 
Unlike the famous Vintage Ports, which age slowly in the bottle, aged tawnies mature gently in large, neutral wood casks. Most are stored in the famous lodges that cover the cool-climate hillside of Vila Nova de Gaia, the main shipping port across the river from Oporto.
 
There are many different styles of tawny—from the inexpensive, fruity Fine tawnies to the bigger, rounder Selects and Reserves—but none are more developed than the tawnies aged 10, 20, 30 and 40 years and named for the average time they spend maturing in huge wooden casks.
 
These older tawnies are elegant, rich and complex and loaded with flavors of dried fruit, toasted nuts, caramel and savory spices. What sets them apart from the ageworthy Vintage, Late Bottled Vintage or Reserve Ports, is that all tawnies are ready to drink upon their release into the market.
 
As a result, aged tawnies are not reserved exclusively for serving after a rich meal in wintertime, but taste wonderful when served slightly chilled as a refreshing afternoon drink or as an aperitif before dinner in spring and summer. When served at room temperature, they also complement rich fois gras, hard sheep's milk cheeses and softer, creamier styles like Brie and Gorgonzola, simple foods like mixed nuts and dried fruits and desserts such as creme brulee, pear frangipane and nut-based tarts.
 
Over the past decade, the overall perception of these lovely fortified wines has changed considerably. A survey by Wine & Spirits magazine found that aged Tawny Ports had overtaken Ruby, Vintage Character, Late Bottled Vintage and Reserve ports as the most popular style served in United States restaurants.
 
The change wasn't caused by the more expensive tawnies either, but by the 10- and 20-year-olds, which range at a very reasonable price of $20 to $50 for a 750 ml bottle.
 
The five main red grapes used to make Tawny Port are Touriga Nacional, Tinta Roriz (also known as Tempranillo), Touriga Francesa, Tinta Barroca and Tinta Cao. Because aged tawnies are made from the highest quality grapes, most come from the premium Cima Corgo zone, located in the middle region of the Douro.
 
Once harvested, the grapes are fermented until they reach 6 percent to 7 percent alcohol, then doses of brandy (77 percent alcohol) are added. The sudden shock of high alcohol kills the remaining yeast and stops fermentation. What's left is the basic structure of a wine with about 18 percent alcohol and an ample amount of residual sugar.
 
As the tawnies age, additional amounts of younger, fruitier wines are added to fill vacant space caused by evaporation; 3 percent per year is common. This blending builds layers of freshness, complexity and ultimately the charm or personality that make these consistent styles of house wines so recognizable to tawny fans.
 
When tasting a soft, silky, aged Tawny Port, it's hard to imagine how such a fragile and delicate fortified wine could be made in a rugged mountainous area like the Douro River Valley in northern Portugal. Yet it's been done for more than 300 years, and the secret is a mixture of passion and patience.
 
There are many different styles of tawny -- from the inexpensive, fruity Fine tawnies to the bigger, rounder Selects and Reserves -- but none are more developed than the tawnies aged 10, 20, 30 and 40 years and named for the average time they spend maturing in huge wooden casks.
 
These older tawnies are elegant, rich and complex and loaded with dried fruit, toasted nuts, caramel and spice flavors. Also important is that all tawnies are ready to drink upon their release into the market.
 
In 2002, a survey by Wine & Spirits magazine showed that aged Tawny Ports had overtaken Ruby, Vintage Character, Late Bottled Vintage and Reserve ports as the most popular style served in restaurants in the United States. Aged tawnies sell well mainly because they are still reasonably priced, ranging from $20 to $35 for a 750 ml bottle of 10-year-old tawny and $30 to $50 for a 20-year-old.
 
The five main red grapes used to make Tawny Port are Touriga Nacional, Tinta Roriz (also known as Tempranillo), Touriga Francesa, Tinta Barroca and Tinta Cao. Because aged tawnies are made from the highest quality grapes, most come from the premium Cima Corgo zone, located in the middle region of the Douro.
 
Once harvested, the grapes are fermented until they reach 6 percent to 7 percent alcohol, then doses of brandy (77 percent alcohol) are added. The sudden shock of high alcohol kills the remaining yeast and stops fermentation. What's left is the basic structure of a wine with about 18 percent alcohol and an ample amount of residual sugar.
 
Unlike the famous Vintage Ports, which age slowly in the bottle, aged tawnies mature gently in large, neutral wood casks. Most are stored in the famous lodges that cover the cool-climate hillside of Vila Nova de Gaia, the main shipping port across the river from Oporto.
 
As the tawnies age, additional amounts of younger, fruitier wines are added to fill vacant space caused by evaporation; 3 percent per year is common. This blending builds layers of freshness, complexity and ultimately the charm or personality that make these consistent styles of house wines so recognizable to tawny fans.
 
The longer the wine stays in the cask, the more the colors change from the original violet and ruby to the more subtle hues of amber and burnt topaz.
 
Once the aging is complete, the wines are blended, filtered, then bottled. The year of bottling appears on each label in accordance with laws imposed by the Instituto do Vinho do Porto, the organization governing wine quality in Portugal. Here are some top Tawny picks:

• Dow's 10-Year-Old Tawny Port ($27) -- Nutmeg and dried fruit aromas; opens up to fresh plummy flavor, caramel with long, sweet finish; fresh and delicate.
• Dow's 20-Year-Old Tawny Port ($49) -- Toasted almonds and orange blossom; sweet fruit and dark chocolate; alluring.
• Fonseca Guimaraens 10-Year-Old Tawny Port ($33) -- Smoke and anise; ripe plum and apricot, Amaretto and spice; ohhh, so elegant.
• Fonseca Guimaraens 20-Year-Old Tawny Port ($50) -- Vanilla, walnuts and tobacco; white raisin, ripe plum and toffee, great finish; long and luscious.
• Grahams 20-Year-Old Tawny Port ($48) -- Leather and maple syrup; dried cherry and berry flavors, dark chocolate, almond paste on the finish; rich and velvety.
• Otima (Warre's) 10-Year-Old Tawny Port ($24) -- Caramel and nutty; dried fruit, molasses, cocoa and long, lingering finish; beautiful and elegant.
• Quinta do Noval 10-Year-Old Tawny Port ($27) -- Liquid form of a cherry cordial; intense.
• Sandeman 20-Year-Old Tawny Port ($48) -- Vanilla, mint and pronounced fruit aromas; apricots, white peach, nuts and spice; unique, exotic.
• Smith Woodhouse 10-Year-Old Tawny Port ($26) -- Complex; forest floor, maple syrup aromas; fresh plums, dried figs and spices; dense.
• Taylor Fladgate 10-Year-Old Tawny Port ($33) -- Vanilla, caramel and cinnamon; apple, pear, stone fruit and black pepper; long buttery almond finish; big and complex.
• Taylor Fladgate 20-Year-Old Tawny Port ($50) -- Licorice, butterscotch and toasted nuts; raspberry, currant and cocoa; a smooth operator.
• Warre's 20-Year-Old Tawny Port ($48) -- Very aromatic with almond notes; brown sugar, ripe raspberry and strawberry dipped in dark chocolate; deep and sensual.