(WSJ) - Throughout the Napa Valley, vintner Dario Sattui is best known as the proprietor of a castle: the 142,000-square-foot, $40 million medieval-style structure that is the site of his second winery, Castello di Amorosa near Calistoga, Calif.

The castle, which opened to the public six years ago, was built with a team that included a European vaulted-ceiling expert, stone masons and fresco artists to help ensure its historical accuracy. Its hand-planed doors were made with hand-forged nails; its bricks and tiles were salvaged from Austria, Italy and Romania; its dungeon is stocked with carefully reproduced medieval torture equipment.

"I'm in the wrong era. I should have been born 200 years ago," says Mr. Sattui, who designed the castle.

It was the same obsession with history that drove the recent renovation of his residence—a Queen Anne-style Victorian home situated just past the grape vines and down the hill from the castle. Mr. Sattui has spent $3.8 million to preserve the home and restore its period details.

On a tour of the house during the September harvest, when the property's vines hung low with purple grapes, Mr. Sattui pointed out period details such as walls decorated with vintage patterned paint rollers, intricately inlaid parquet floors and an ornate 1870s square grand piano that came with the house.