The only sin in Chicago is thinking small. Already crowded with great structures, the city has yet again become a magnet for big-name architects, igniting a new wave of bold building. Blair Kamin explains why this "second city" is second to none

Say Chicago to people around the world and they are almost sure to conjure up a stale set of images, from Al Capone riddling his rivals with bullets to Michael Jordan soaring through the air. Or perhaps they'll come up with a blank slate. "Famous for being the automobile city, right?" a clueless fellow in Beijing said to one of my Chicago Tribune colleagues this spring, confusing Chicago with Detroit. Old legends die harder than old gangsters. Although Chicago beat out more glamorous Los Angeles in April to become the U.S. candidate to host the 2016 Olympic Games, it remains our most misunderstood—or maybe our least understood—big city.

A more accurate snapshot of Chicago can be found within brown-bag-lunch distance of my office, in Millennium Park, the twenty-four-acre, $500 million pleasure ground that unfurls at the foot of the city's impressive cliff of skyscrapers. I always start at the Crown Fountain, where barefoot kids race through a shallow reflecting pool toward the twin fifty-foot-tall glass-block towers that flank it. Enormous images of human faces are projected on the towers' sides, and every few minutes the giant faces spit an arcing jet of water into the pool, rewarding the kids with a free shower and making even gray-suited business types break into a smile. The joyous scene doesn't just offer a modern version of medieval gargoyles. It's a new kind of public space, raucously interactive rather than primly static. And it presents a vivid symbol of Chicago's postindustrial renaissance.

These days, construction cranes are putting up so many high-rise hotel and condominium towers, including a 92-story glass-sheathed behemoth by the flamboyant New York developer Donald Trump, that Chicago could be rechristened Shanghai on the Prairie. Architecture's globe-trotting stars have joined the game, including Santiago Calatrava, who recently won approval for the Chicago Spire, a 150-story condo tower that could someday twist into the sky like an oversized drill bit. If its developer can come up with the money to build this two-thousand-footer, the Spire will become North America's tallest building—a fitting superlative for Chicago, the city that invented the skyscraper in 1885.

That was only the beginning. Within decades, masters of the drafting board such as Louis Sullivan, Frank Lloyd Wright, Daniel Burnham, and Ludwig Mies van der Rohe had introduced the Prairie-style house, the Beaux Arts civic center, the steel-and-glass high-rise, and countless other modern archetypes. The legacy of these design demigods is deeply felt here. As you walk through the compact downtown, their buildings surge into the foreground, a gathering of masterpieces.

But while Chicago is an extraordinary destination for architecture, its ultimate allure arises from the crackling tension between its soaring skyscrapers and its rogues' gallery of civic imperfections. This is no shining city on a hill, and not just because of the gridiron-flat Midwestern landscape. For years, Chicago was home to both the world's tallest building, the 1,450-foot Sears Tower, and its largest housing project, the Robert Taylor Homes, which stretched like filing cabinets for mile after heartbreaking mile.