(WSJ) - Prominent Napa Valley vintner and Dean & Deluca owner Leslie Rudd and other investors bought Clos Pegase Winery on Tuesday, promising to expand and improve the vineyard known as much for its art and architecture as for its wines.

Clos Pegase founder Jan Shrem was one of Napa's first winemakers to spend heavily on the design of his winery three decades ago, when he and his late wife tapped the San Francisco Museum of Modern Art to help organize an architectural competition for their new building. Architect Michael Graves's winning design is a postmodern landmark of the region.

"Clos Pegase put Napa on the map architecturally," said Mr. Rudd in an interview. He bought the winery with Vintage Wine Estates, a group of wineries based in Santa Rosa, Calif., in which he is a partner. The purchase price wasn't publicly disclosed but the buyers pledged to improve quality and increase production at Clos Pegase. Mr. Rudd also owns Rudd Winery in Napa and other businesses involved in food and drinks.

The deal is the third significant sale of a Napa winery this year. In April, longtime vintner Bob Travers sold his Mayacamas Vineyards to private investors including former Screaming Eagle Winery and Vineyard owner Charles Banks. Last month French billionaire François Pinault bought Araujo Estate Wines. Terms weren't disclosed for either transaction.

Mr. Shrem and his wife began producing wines on 50 acres in Calistoga, Calif., in 1983 and its wines are generally well-regarded. But the winery's art and architecture have long been its main draw for tourists. Mr. Shrem, now 83, decorated the estate with his large art collection, which includes a 17th century Italian fountain and a sculpture by Henry Moore. The artworks aren't part of the transaction, Mr. Shrem said.