Finally, in 1998, they bought their house. It took two years to rebuild the rundown property, so, in the meantime, they stayed in a makeshift accommodation and learned the hard way about local regulations.

At one point they were told they could not build on the site at all, but then it was discovered that officials had mistaken the Lupers’ house for another building. Then they were told to move the house three meters from a wall, so the architect had to redraw his plans. And they had to get special permission to paint the house something other than white.

The 326-square-meter (3,510-square-foot) house, at the top of a steep drive, was rebuilt in traditional style with red tiled roof, wood-frame windows and shutters. A large terrace and balconies offer views down to the river and up to the vineyard. The property also has fruit and olive trees.

The house has a 75-square-meter (807-square-foot) living-dining room next to an unusually large 64-square-meter (689-square-foot) eat-in kitchen. There also are two bedrooms with bathrooms and a small office/guest bedroom, a third bathroom and a pantry. The house has under-floor central heating, connections for satellite television and Internet service, and a two-car carport.

Mr. Luper renovated the winemaking cellar below the house, but kept the old lagares, or tanks, where workers tread on the grapes. “We do it the traditional way, unlike in California where they use mechanical treaders,” he said.

In 1999 the Lupers’ first Quinta da Carolina vintage won praise in Europe and the United States. The winery now produces 4,000 to 6,000 bottles of red table wine a year, most of which is sold in the United States for $40 to $50 a bottle.

While the winemaking effort has been satisfying, the Lupers say living in the Douro has been less so. The couple have found it hard to make Portuguese friends in the rural community, and there are few expatriates in the area.

“We’re the only Americans here,” Mr. Luper said. And Mrs. Luper added that she misses their children, four of whom are in California and Oregon. The youngest, a daughter, is in Geneva, working for the Red Cross.

Mr. Luper, who says one of the reasons for selling is to have more time with their family, hopes to attract a foreign buyer who will appreciate the house’s stunning location. There are few wineries for sale in the area, he said, and prices are low compared with winemaking regions in Europe or the United States.

Mrs. Luper said that a friend in the real estate business in the Napa Valley confirmed her belief that “what we offer would sell for approximately $4 million to $5 million, or 3 million to 4 million euros, in France.”

On the positive side, Mr. Luper said, “We took a very rough place and made it something nice.” And Mrs. Luper added, “We did it against the odds. I always had a romantic dream and we did it.”