Rumor Has It: Mark Ruffalo knows more than his fair share about San Francisco's restaurants and Beat Generation past. It's not just a rumor.

"San Francisco is four cities, not just one," says Mark Ruffalo. "It's one-third Hong Kong, a third Paris, and a third New York, set on seven hills, just like Rome. It's all against the Pacific Ocean, the biggest ocean in the world." On another movie set in another city, the classically trained leading man with the skyrocket­ing career is talking about how he fell in love with San Francisco. He was filming Just Like Heaven, this year's supernatural comedy in which Reese Witherspoon's spirit pursues him through the city of the seven hills. "That's when I really got an idea of what the city was all about," he says.

He had first visited on a junket to promote his breakthrough hit, You Can Count on Me, in which he turned in a searing performance as the bad-boy brother of Laura Linney, but he spent most of his time in a hotel room. But then two roles brought him back for an extended stay: first, Heaven, and, most recently, to scour the city as a detective in director David Fincher's forthcoming film, based on a true story costarring Jake Gyllenhaal, Robert Downey Jr., and Anthony Edwards. Ruffalo plays the San Francisco homicide detective tracking the Zodiac serial killer, who terrorized San Francisco for 25 years and who remains at large. During the filming of both movies, Ruffalo saw the city like an ordinary person, instead of like a star, heading out alone with his scripts, disappearing, as always, into his role, getting tips from locals he met in restaurants as he rehearsed his lines silently while eating dinner at the bar.

This month, he's back in Rumor Has It, a loosely based sequel to the 1967 classic The Graduate, costarring Jennifer Aniston and Kevin Costner. But Ruffalo left his heart in, well, where else? From playing everything from a bachelor chased by a blond dervish to a detective chasing a serial killer, Mark Ruffalo got to know San Francisco not from the hotel suite, but from the streets. Here are the secrets of the city he uncovered.

The city has so many cultural influences, you must have found some excellent restaurants. What were the more memorable ones?
I stayed at the Ritz-Carlton, which has the Dining Room, a fantastic, five-star French restaurant. It's down in the lobby, and it has a sort of Southern feel to it. I mean, a little bit of an English, upper-class feel. They have an amazing foie gras, and they'll bring you a paper if you show up by yourself for dinner. Very friendly people.

You ate alone?
I ate alone quite a bit.

You never think about actors eating alone.
Well, you know, my family's not with me. I usually am working and working on my lines, so I spend a lot of time alone. So, I will eat alone often. I went to another place in San Francisco with Reese called Quince, which is an amazing little Italian restaurant. It's a small room; it's very elegant, a little bit looser than the five-star at the Ritz. It's a husband-and-wife team. The kitchen is connected to the back of the building and goes downstairs into, like, a basement area. It's a very French country feel - very open, you know, 15-foot ceilings. The husband's the chef. It's very accommodating, kind of a homey feeling, with the most delicious Italian food. They have a quince salad that is amazing. They have really wonderful handmade gnocchi, with the thumbprints on them. They're really light and perfect, made with very little flour and egg, which is, I think, one of the strong suits of a great gnoc­chi. It has a really wonderful wine list, with Northern Italian wines. It's pretty small and kind of an exclusive place.