Napa Valley is, of course, a producer of world-class wine. But a very different kind of liquid, bubbling deep under the surface, also draws visitors to a 35-acre attraction near Calistoga -- Old Faithful Geyser of California.

"Basically there's a cold-water stream hitting hot lava way down deep," staffer Ginger O'Byrne says, "and it builds up pressure and it goes off."

Unlike the most famous Old Faithful in Yellowstone National Park, this one is privately owned, bought years ago by a school teacher from Santa Rosa. But they both spew water on a schedule you can pretty much set your watch to, with a few exceptions.

"It changes depending on rain, groundwater, if we've had earthquakes," O'Byrne says. "We usually pick up a 250 mile radius, if there's an earthquake, it'll hold off, it won't keep its same pattern. Gets a little bit erratic. Right now it's 35, 40 minutes, stays up about five minutes, and it averages about 30-60 feet."

The water reaches 350 degrees when it comes out.

"But there's nothing to keep it warm," O'Byrne says, "so it doesn't feel hot when the spray hits you."

A crowd of 20 or so slowly gathers and waits. And then, more or less on schedule, steam and water begin burping and bubbling out of the geyser. Finally, a stream of water explodes about 50 or 60 feet into the air.

People come from all over the world come to watch this geothermal performance. Eric Tarfoot is visiting from the Netherlands.

"All of a sudden it comes out of the ground and you get all this water," he says. "You don't know why it is. It's something geological, but you don't know what it is."

Youngsters Ben and Adam are visiting from the Bay Area city of San Ramon.

"It was pretty cool," Ben says. "It was a little different."

"I was thinking of it going a little bit higher," Adam adds. "That was actually cool."

Others aren't quite as impressed. Marla Wolf is visiting from nearby Oakland.

"It was all right. It seemed a little expensive for what you get, I think," Wolf  says.

Her husband Anthony adds, "You know, after two or three wine tastings it probably looks a little more fascinating than it really is."

But if you're put off by the price of admission --  it's $10 for adults, $7 for seniors and $3 for kids -- there's more. Ginger O'Byrne shows us the fainting goats.

"These two guys right here are the oldest guys, been here nine years, O'Byrne says. "And these are one of our babies, baby fainters."

O'Byrne explains the goats faint when they're scared or excited.

"When they play they'll scare each other, especially when they're little. They'll both just fall over and feet go up in the air, and they're back on their feet within a minute. They get back up right away. They look kind of dead sometimes."

On this day, the goats do not faint. In fact, they're downright talkative, despite the 90 degree weather.