Cusack is calling from a hotel in Los Angeles in the middle of a daylong studio promotion for Must Love Dogs, the romantic comedy in which he stars this month with Diane Lane and Dermot Mulroney. He says he's had a very long day, filled with one interview after another, with photo sessions interspersed.

"So, we're going to talk about Chicago," I say, and I can hear him brighten.

"Hit me," says Cusack.

And he's off and riding. Cusack has a home in Los Angeles, but when you're from Chicago, you're a Chicagoan until the day you die. He has a place downtown, and on his first day or two back, he usually wants to see everything at once.

"I'll ride up and down the waterfront, go by Navy Pier, then all the way down the public park toward Montrose," he says, ticking off a multiday biking itinerary. "You can go all the way up and down Lake Shore Drive. There are parks all over there. Then you can go through the city and all of its different neighborhoods - Wrigleyville and near Halsted, everywhere. You can go up toward the South Side, toward Millennium Park, to the Shedd Aquarium and Soldier Field, through Chinatown, and all the way back through the city to the Loop, and then through downtown."

He could practically bike through Chicago­ blindfolded. "I know the city inside and out," he says. "I don't think there's an area I haven't been to."

Then he begins directing me: "There is a tour where you can go up and down the river and see the architecture there - it's just out of control."

He's talking about a boat tour called Chicago from the Lake, which hits the highlights of Chicago architecture. But Cusack prefers the bike to the boat. "You go past the Wrigley Building," he says of the circa-1921 terra-cotta-clad edifice that's known as the gateway to the Magnificent Mile, one of the greatest shopping streets on earth.