Since Craig and Kathryn Hall bought their first Napa Valley vineyard in 1995, they have made a huge imprint on the face and the culture of the valley.

In the past 12 years they have purchased a total of 3,300 acres of land in Napa and Sonoma counties, about 500 of which are planted to winegrapes; built a winery in Rutherford; and in 2003 purchased a winery facility in St. Helena.

On Friday, they broke ground for their most ambitious venture yet.

More than 300 dignitaries, neighbors and guests turned out to join them as they revealed the design of their planned winery on the St. Helena property, former site of the old Napa Valley Co-op winery and more recently the location of Golden State Vineyards.

The Halls were joined by Frank Gehry, the renowned architect who designed the facility, and Edward Chan, who was instrumental in the design team.

Among those present were Robert and Margrit Mondavi, and Margrit moderated a brief panel discussion with the Halls, Gehry and Chan. “It takes me back a little to when Robert was building his winery (in the 1960s),” she said. “It was the first new winery after Prohibition. There was so much excitement and interest ... this is the beginning of a new era.”

The long-awaited unveiling revealed a tasting room that will feature an undulating trellis-like roof, which, Gehry said, makes the connection with vineyards and agriculture and “complements the natural setting of the Napa Valley.”

“The new Hall Winery will be an experience that is unique and harmonious with the beauty of the Napa Valley,” Chan said in a statement that was part of a slide show previewed by guests.

The winery will encompass 130,000 square feet, in several buildings, but the big attraction will be the 10,000-square-foot tasting room, which will be covered by the trellis-like structure. It will be the third stage of the project and is expected to be completed in 2010. The first part, the site work, has already been completed, and work will start soon on the production buildings, which are expected to be finished by next summer.

Craig Hall declined to state the exact cost of the project, but acknowledged that “it’s more than we thought, and it keeps going up.” Asked if it was more than $100 million, he smiled and replied, “That’s safe to say.”

Gehry said his firm is working with two concepts on the construction of the trellis roof — one will be wood, the other a cement that “comes out like paste, it’s soft and when you lay it out on something, it takes that shape.”

Gehry then joked, “Maybe we can put a little wine into the concrete mix and give it a little color.”

Mike Reynolds, president of Hall, said that two types of wood are being considered — one laminated, the other a solid wood that will be bent into shape.

“When people heard you (Gehry) were going to be involved, everyone thought it would be a titanium winery,” said Kathryn Hall. Gehry has become known for his use of titanium in his designs, but he said he has used it on only two projects.

“It’s very costly,” he added.

To preserve the long history of the property, a small building that was constructed in 1885 will be renovated and will serve as the central point in the center of the courtyard, Craig Hall said. The building was hidden inside other existing buildings, and few people knew it was there, he said. At one time during the late 1930s and 1940s the facility was responsible for about 40 percent of all wine produced in Napa Valley.

Referring to the site’s history, Gehry said, “We want to be inspired by the past, but not copy it. The trellis for example — we didn’t start out to make the trellis the most important part (of the design) but it worked out that way.”

The winery sits on a 33-acre parcel and is permitted for 500,000 cases, Reynolds said, but he expects “the first build-out will be about 200,000 cases.” The winery in Rutherford was designed to produce small production lots, he added. Richard Batchelor will remain as winemaker.

To give visitors an idea of the lengthy process the Halls and Gehry went through to arrive at the tasting room design, an entire wall of one area of the current barrel room in the existing building is devoted to a display showing the progression of design concepts for the tasting room from the first go-around to the final version.

Gehry, whose work is world-known and includes such projects as the Guggenheim Bilbao in Spain and the Walt Disney Concert Hall in Los Angeles, was approached by the Halls in 2003. “I knew the Halls weren’t coming here to rape the place or make a killing,” Gehry said. “The inspiration (to design this) came from them, from the land and the program.”

His associate Chan added, “It didn’t take much convincing. We could make this an art-friendly place. You have wine, art and beautiful landscape — what more could you want?”

“We hope this will be a piece of art,” Craig Hall said. In addition to its aesthetic design, it also will be eco-friendly, with installation of photo-voltaic cells on the roofs of the production and barrel storage buildings, and Hall said the winery will “use a 5,000-year-old gravity flow system (to move wine) but will incorporate modern technology.

This will be the first winery built from a Gehry design. His firm designed a winery in Canada several years ago, “but it was never built,” he said.

The project has not been without controversy, though. When the initial proposal was made to the county in 2004, nearby residents and some local politicians voiced concerns about increased traffic, gawkers who would slow down on Highway 29 to look at the winery, and even concerns about the design of the winery itself.

“We did a bad job of communicating what we were planning,” said Reynolds. “But we listened to the concerns, met with the people, developed the proposal with changes, submitted it in April 2005 and it was approved in January 2006.” The tasting room will not be visible from the highway.

The groundbreaking didn’t really involve breaking ground. Instead, the Halls, Gehry and Chan each tossed a shovelful of dirt into a hole where a tree had been planted in front of the proposed tasting room site. Guests didn’t mind — they were cooling off in the barrel room watching the proceedings on two giant television screens.

Bu clearly, the star of the show was the proposed tasting room.

“At the end, when you look at the finished project, you think, ‘It’s a magic trick,’” Gehry said. “You don’t remember how or why you did things. You just did them.”

Features Editor Sasha Paulsen contributed to this story.