Costello, 62, a retired high school drafting and architecture teacher, has lived in the city since 1964 and has led tours since 1990. "I call Chicago the architecture capital of the world because of the variety here," he said. "There's every style from Roman to Greek to Egyptian to Modern."

He's passionate about buildings. When you ask him if he's a Cubs fan, he says, "No, I'm a Wrigley Field fan."

Wright's Robie House

Architects and architecture firms are about as well known here as Confederate generals in Richmond, Va. By the time we headed to Hyde Park, we had already become familiar with the names that Costello tossed around during his tour: Daniel Burnham (his motto was "Make no little plans"), most famous for his monumental 1909 "Plan for Chicago"; Ludwig Mies van der Rohe ("Less is more"), one of the fathers of the modern "glass box" skyscraper; Louis Sullivan ("Form ever follows function"), whose design firm helped rebuild the city after the Great Fire; and of course, Frank Lloyd Wright, the nation's architecture icon, who created the uniquely American "Prairie" style, with its distinctive low profile and horizontal lines.

Hyde Park was the site for Chicago's 1893 World's Columbian Exposition, famous for the first carnival midway and the first Ferris wheel. Today it's known as the home of the medieval-looking University of Chicago, one of America's most beautiful college campuses. Our main objective, however, was the Robie House, designed by Frank Lloyd Wright and built in 1910.

Before we arrived, Judith Kambstad, who sat in the row across from us on the bus, had already given me a Robie House pep talk. Kambstad, who's retired and lives in Tustin, loves Frank Lloyd Wright. "When I saw that the Robie House was on the tour, I had to come," she said.

With little prompting she could reel off plenty of Wright facts. For example, he worked as a draftsman in Sullivan's firm, was never formally trained, and "he called himself the world's greatest architect."

The Robie House, with its tunnel entrance, hidden front door and low-ceilinged foyer, seemed claustrophobic and uninspiring. But as we walked to the second floor, it opened up. The dining room was airy and light, its details, such as the light fixtures and windows, filigreed with wood detailing. "I could take this whole floor home with me," Kambstad said. Judging by the oohs and aahs, most of the tour-goers agreed. Wright's questionable marble conversion of the Rookery Building was forgiven.

On our way back to the city, we wound through the neighborhoods of Kenwood and Bronzeville, passing the former home of Muhammad Ali and the current compound of Louis Farrakhan as well as a synagogue-turned-church where gospel great Mahalia Jackson used to sing.

Then we passed through the college campus of the Illinois Institute of Technology. The IIT, designed by Mies van der Rohe, is as spare and modern as the University of Chicago is ornate.

Mies van der Rohe, onetime director of the Bauhaus school in Germany, fled the Nazi regime in the 1930s and eventually ended up as the head of the IIT's architecture program. He designed about 20 campus buildings and it's easy to see how his "less is more" motto comes into play. The style is pure Bauhaus: sleek, unadorned, simple and made of concrete, steel and big sheets of plate glass. The main building, Crown Hall, is simply a half-acre open room with low, movable walls to create rooms and workspaces.

The most striking IIT building, completed last year, was designed by Dutch architect Rem Koolhaas. The city's elevated train system, the "El," cuts right through the campus. To muffle the roar of the trains, Koolhaas, who also designed the student center, encircled the tracks with a giant metal tube, making it look like something out of a sci-fi book.

Our final stop was a photo op by Chicago's John G. Shedd Aquarium, which sits on a point jutting into Lake Michigan and affords a sweeping view of the city. Jody zoomed in and out on the scene with her camera, but it was useless. The city is too expansive, too complex for a long-distance shot to do it justice. It's like trying to photograph a crazy-quilt from a block away.

When the bus let us off back at the ArchiCenter, the sky was still grim and we could feel a few sprinkles. But as we walked into the city, Jody remembered boat-trip docent Hebert's final words: "I hope you'll remember to look up."

We did and even the gray sky couldn't rain on Chicago's grand architectural parade.

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Finding the urban heart

GETTING THERE:

From LAX, nonstop service to Chicago Midway is offered by Southwest and ATA; connecting (change of plane) service is available on Northwest, Airtran and Frontier. Nonstop service to O'Hare is available on American and United, with connecting service on Delta, America West, Continental, US Airways and Northwest. Restricted round-trip fares begin at $138.