City Hall, as a building, is ornate, pompous, outsized, French, and hasn't looked this good in decades. City Hall, as an institution, is many of those things, though French and fetching aren't among them.

Almost every aspect of City Hall, like its tenant's pet projects, took longer and cost more than planned, $3 billion in contemporary currency.

The nation's largest municipal structure, 14.5 acres of floor space, required 30 years to build, an eternity. This year marks the sesquicentennial of the design by architect John McArthur Jr., who had the misfortune to die 11 years before its completion.

"Silent, weird, beautiful," Walt Whitman observed coming upon the still-uncompleted structure one night, "a majestic and lovely show there in the moonlight." By the time City Hall was finished in 1901, its wedding-cake Second Empire style had fallen out of fashion.

Restoring the building hasn't been a breeze, either, demanding almost 20 years of work, mostly on the exterior. The tower required six years and in excess of $24 million; the facades, scheduled for completion in 2012, a dozen years and $80 million.

"Walt Whitman got the essential bizarreness of the building," says Williams College art historian Michael J. Lewis, who will give a lecture on the building's history Thursday at the Wagner Free Institute of Science, another McArthur design. "City Hall takes one of the great swaggering styles of all time, this French style of pomp and power, and applies it to one of the world's most democratic town halls."

In a quintessential American city, founded by Quakers respectful of the quiet integrity of plain spaces, then developed by democratic fathers who embraced the grace of redbrick federalism, City Hall's baroque opulence serves as a massive rebuttal to the past. It's the antithesis of the meeting house and Independence Hall, yet welcoming to all. It has no front, but four equally grand sides.

"It was built to be the biggest, the best, the tallest, the most ornate, to show the world that this city was among the greatest cities in the world, the top of the heap," says Hyman Myers, who served as the building's lead restoration architect. By the time it was finished, the Washington Monument had already eclipsed the 548-foot tower in height.

"The rooms inside are just the finest. The building is indicative of the city's pride," says Greta Greenberger, who has been conducting two-hour weekday tours for 18 years. "They built it because they could, because it was such a successful city."

Today, City Hall seems even more of an anachronism, a European palace in a city that celebrates a working-class, rowhouse sensibility. Many of Greenberger's tour participants are foreign, appreciative of what many citizens take for granted and view as the world's most decorative subway shed.

The restoration results have been so extraordinary that Philadelphians forget how dreadful the place looked for so many decades: covered in grime, scaffolding, and several tons of pigeon waste. During decades of neglect, the building mirrored the city's slow economic decline. People forget, too, that City Hall was marble, white, graced with 250 Alexander Milne Calder sculptures. They forgot it was exquisite.

Today, City Hall is both glorious yet elegiac, trumpeting a monumental future and continued triumphs that were not to be. The building stands as a florid reminder of what Philadelphia once was, and what might have been, of all the manufacturing, wealth and civic optimism for growth, a city that never quite met up again with the grandeur of its municipal structure.

"The city is not what it used to be not because of the government, but because the times have changed," Myers says. "There's not the work there was when Philadelphia was, literally, the workshop of the world."

It's not City Hall that got small, only the city's industry and outlook.

City Hall is a municipal cathedral, sitting squarely in the town center. "Like a cathedral, once you're done, you're fixing up the old part," Lewis says. In the 1950s, the building was an industry, employing almost 500 full-time tradesmen, including plumbers, electricians, masons and upholsters. Today, there are only 14.

For many years, City Hall was despised for being so grand and old-fashioned, outsized and in the way. Its critics were legion. "The most disreputable and disrespected building in Philadelphia," the architect Louis I. Kahn once adjured. A white civic elephant, there were plans for private shops, businesses, even a casino.

City Hall, the institution, lumbers on, turgid, obstinate, outsized, provincial and slow. But City Hall, the building, thanks to years of labor and investment, is again as beautiful, shiny and grand as Philadelphia's old heroic vision.

Karen Heller: More Information

"Silent, Weird, Beautiful: Philadelphia's City Hall and Its Architect" is at 5:30 p.m. Thursday at Wagner Free Institute of Science, 1700 W. Montgomery Ave. Admission is free, though a donation of $10 is suggested for those 12 and older. For more information: wagnerfreeinstitute.org

City Hall offers two-hour tours at 12:30 weekdays, beginning in Room 121. Tickets are $10 for adults, $8 for youths and seniors.EndText

Contact columnist Karen Heller at 215-854-2586 or kheller@phillynews.com.