SAN FRANCISCO -- From a distance, it looked like -- pardon the pun -- a giant ant farm, creatures big and small crawling over the sprawling colossus that is AT&T Park.

There was no game on Saturday, as the field was covered with mounds of dirt, but the corridors and green seats and walkways were happily populated with baseball fans attending the KNBR 680/Giants Winter FanFest.

More than 20,000 fans were on hand, easily topping the estimated crowds of some 6,000 that crammed into Pier 48 in years past.

Giants president and managing general partner Peter Magowan seemingly saw everyone while cornered on a ramp and signing autographs for about an hour.

"Before we came here today, my wife said she doesn't like crowds," said Magowan amid the ring of fans. "But I love it when they come to the ballpark. Today is great."

Executive vice president Larry Baer was his usual exuberant self, but he was definitely pleased with the massive turnout for the annual event, also sponsored by the Scottsdale Convention & Visitors Bureau.

"It was very successful, and you can judge that by reading the fans' faces -- they were all smiles," said Baer after the deluge of aficionados toured areas they've never seen before -- dugouts, the press box, radio booths and clubhouses -- and stayed in long lines to get autographs of players.

"Next year, we hope to have grass on the playing field -- we'll have the Emerald Bowl again next January -- but try to schedule it so we at least have a football field," said Baer. "That's better than dirt."

Perhaps the biggest draw of all this day was new left-hander Barry Zito, the former A's star now signed to a seven-year pact, and Baer said that the response to the hurler has been enormously positive.

"The fans really wanted to see players like Rich Aurilia and Zito up close," said Baer. "Zito has a huge passion for the area, and his signing has given everybody an emotional lift."

Groups crowded the corridors to purchase season-ticket packages, search for food and souvenirs and watch the live feed of Giants flagship station KNBR announcers interviewing players.

TV monitors and the soon-to-disappear scoreboard screen -- it will be replaced by a high-definition scoreboard by Opening Day -- also displayed the interviews.

Parking was of game-day proportions, but Tony Souza of Atwater, Calif., some 140 miles away, had a handicap sticker that proved handy.

"I've been a Giants fan since I was 4 years old," said Souza, who purchased a bat inscribed with his name. "It's crowded but fun. I saw Dave Righetti and Bruce Bochy at the question-and-answer session. That was pretty cool."

San Francisco resident John Trevitnick, who was with daughter Zoe, 2, and son Ian, 7, agreed it was "a little crazy" being in the ballpark, but still was enjoying the tours.

"The kids are having fun," he said.

Eight-year-old Josh Forshaw of Livermore, Calif., waited patiently in line to participate in batting practice while father Jack and mom Dianna stood by.

"We just got here, but it looks fun," he said. "I've been a Giants fan all my life."

And, yes, Magowan eventually extricated himself from the fans, but with his orange sweater and familiar silver hair, he had a trail of autographs seekers trailing behind.

How was the day, boss?

"Wonderful," said Magowan.