Between the city's gleaming financial district and red-bricked North End, just a few hundred yards from the site of next week's Democratic National Convention, unused pipes and palettes of wood litter block after block of city streets.
They are probably the most famous construction leftovers in the world.
For a city desperately working, even now, to put on a Sunday polish for a week of national attention, these reminders of the historically expensive and divisive Big Dig are alarmingly visible.
During the convention, the city will point to the near-complete megaproject as a symbol of a visionary "New Boston," a city that is brainy, innovative, progressive, and tolerant - part Athens, part Silicon Valley, part Greenwich Village.
But that's just one side of Boston's persona, and the Dig also symbolizes flaws in this city's character - from neighborhood turf wars to political cronyism that critics cite as a factor behind the project's huge cost overruns.
And beneath all that, the Dig encapsulates in 2004 a tension that has characterized this city since colonial days: the struggle between tradition and innovation.
That tension emerged as soon as the Puritans debated how best to retain the purity of their holy experiment amid the influence of commercial trade and modern comforts.
A fateful intensity, it seems, has always characterized Bostonians' struggle to shape their city. As John Winthrop, the city's first leader wrote, Boston was meant to be a "city upon a hill," an example for the world.
Today this metropolis, arguably more than any other major US city, still wrestles with how to preserve its historic character and close-knit neighborhoods while also striving for the elusive prize of being a world-class city.
As delegates gather next week, literally in the shadow of Boston's new answer to the Golden Gate Bridge, this is the context of Boston's 2004 biography.
"I think we're really at a crossroads," says Robert David Sullivan, associate editor of CommonWealth magazine. "Boston is divided between people who want it to become a dynamic world-class city, and those who want it to retain its small, local character."
The Big Dig was designed to cut through the tangle of outmoded highways and under the archaic maze of winding streets, allowing Boston's business to flow at 21st-century volume and velocity.
The Dig's tunnels and suspension bridges have eased congestion somewhat. And the project paves the way for a new greenspace, where trendy shops and luxury condos may prosper.
But this is all part of a longstanding, and often controversial process. As the city has welcomed an influx of urban chic in recent years, many believe the city's modest, working-class character could vanish.
Many of Boston's contradictions are embodied in its mayor, Thomas Menino, a quintessential city boss whose bearing seems more suited to construction than the capital.
Mayor Menino is from the neighborhood of Hyde Park, and "Da Mayor" has established his political base, block by block, among the working class.
Yet Menino is clearly trying to forge a legacy based on big ideas. It was under his watch, after all, that the Dig seemed to near completion, and he remains the steward over hundreds of real-estate projects sprouting across the city.
He's also a salesman who spends much of his time wooing engines of the information economy, of which Boston, he argues, is the vital part. The city leads the nation in major hospitals, medical schools, and biotechnology firms. In recent years, Boston has attracted more funds from the National Institutes of Health than any other city.
And then there's Harvard, the Massachusetts Institute of Technology, and the 70 other colleges and universities that call Boston home - and pump $5 billion into the local economy each year. On this plane, Boston can be compared to history's great centers of learning - a modern-day Alexandria, nestled by an East Coast bay.
Of course, life-sciences jobs go to those who wear surgical scrubs, not blue collars. And it's the working class that, despite an old-boy-network of neighborhood pols, increasingly feels left behind. One example: a key city police union is set to picket outside the convention hall next week because of low salaries.
State budget cuts in the arts, education, and public health have hit Boston's poor particularly hard, leaving the city with fewer resources to fight drug addiction and homelessness.
The consequence, say public-health advocates, is a startling ratio of 5 black infant deaths to every 1 white infant death - twice the national discrepancy. In Mattapan, a primarily low-income, minority neighborhood, median household income has fallen 17 percent, to $32,000, since 1990.
For the most part, local disaffection stems from a surge in redevelopment. In Chinatown, for instance, anticipation of the new Rose F. Kennedy Greenway has sent real estate prices soaring, and longtime residents worry about the phasing out of institutions they've known for generations.
"Buildings that were right on the edges of the [interstate] were "C" class," says Robert Brown, a partner with the Boston architecture firm CBT. "Now these same buildings have become ideal for new residents."
Major forces of change are sweeping through virtually all of the city's tight-knit neighborhoods: For the first time, more than half of Boston residents are minorities, drawn by service jobs in universities, hospitals, hotels, and restaurants.
In the East Boston neighborhood, for instance, an influx of Cape Verdians, Brazilians, and Haitians are changing the makeup of formerly Irish and Italian schools and parishes. The last decade saw the white population here drop by 26 percent, becoming just half of the overall population. Meanwhile, the Hispanic population has more than doubled.
But this historically divided city is in some ways growing more tolerant. And for all its images of discord, there are built-in shock absorbers here to help overcome its gulfs.
Several East Boston organizations have gone out of their way to welcome leaders of the Brazilian community into their ranks, a show of respect that would have been unheard of a century ago, says Boston City Councilor Felix Arroyo, whose own election last year was a historic act of unity. While Latinos represent 13 percent of the city's population, half of them are too young to vote, and half of those who are old enough are not yet US citizens. Nevertheless, a coalition of moderates, liberals, Latinos, blacks, gays, and lesbians, along with liberal and moderate whites, banded together to elect Mr. Arroyo, who was born in Puerto Rico, to an at-large position on the council.
"In the past, all ethnic groups had to wait until they could elect their own [officials]," he says. "My election shows that it's a very different Boston."
South Boston - Irish, proud, and insular - has proved more stubborn. Like the area around the Big Dig, "Southie" has seen massive redevelopment and construction, and the first signs of gentrification. Residents complain of a half-dozen new coffee and pizza shops, banks, and dollar stores popping up where they live.
To Dave Errico and Jessica Chandler, standing outside the P.S. Deli on Broadway Street on a recent Sunday, it's nothing less than a disgrace. "They're making condos out of churches," says Ms. Chandler. "It used to be a family neighborhood, but it's lost it."
Yet a fresh start for this historic enclave appeals to those whose emotions are still raw after decades of attempted racial integration. Even after forced school busing began more than 30 years ago, residents deeply resent "Southie's" reputation as a redoubt of white, Irish prejudice, an image born in part of years of intimidation of the black students who attended school here.
"These communities are doing everything they can to help alleviate that stereotype," says Richard Finnegan, a political science protfessor at Stonyhill College in Easton, Mass.
Yet Boston is also a city that prides itself on being socially progressive, always infused with a sense of anguished intellectualism. There are 3,000 nonprofit groups and more cultural organizations per capita than both Chicago and New York. But still, after 30 years, experts say the schools remain segregated, and relations between whites and blacks are strained at best.
In recent years, though, the problem of race has not dominated media coverage. Instead, the most recent spotlight has fallen on another fundamental Boston presence: the Catholic Church.
The clergy sexual-abuse scandal and the archdiocese's decision to shutter nearly one quarter of its parishes here have marked a low point in the history of Irish Catholicism in Boston, and perhaps in America.
But like so many other American institutions, the Church is receiving new life from immigrants. Even as French Canadian, German, Irish, and Italian Catholics move to the suburbs, a surge of Latinos is renewing the Church's mission, and parishes have grown far more flexible than in years past.
"A century ago, when immigrants like Italians came, the Church would say: 'They should learn to speak English and follow established customs,' " says Boston College history professor James O'Toole. "Now, priests are taking language classes to minister to their new members. It's quite a shift."
Boston's Irish, meanwhile, have achieved a new standard of success after dominating city politics for more than a century. Guys named Finneran and Flaherty still occupy the city's political thrones. Catholics make up more than half of the state legislature.
But it's the Irish population's newly won financial power and its historic symbolism that seems to put a smile on the face of so many. Several prominent Irish Catholics, many of them graduates of the Jesuit school Boston College (BC), now lead a stable of major Boston companies. Among them: the financial services firm Fidelity, the advertising firm Hill Holiday, and until a few months ago, Fleet Bank.
BC grads recently took pride in occupying their new alumni club in Fleet's neck-craning downtown headquarters. For an ethnic group long excluded from the waspy business culture here, the club is a potent symbol of Irish achievement. And according to one alumnus, there's a special pleasure in looking down at the Harvard alumni club across the street.
If Boston remains a somewhat divided city, the Red Sox have become a vital force in bringing people together, infusing the city with a passion that's almost unfathomable for other teams.
Bostonians obsess over the Sox for several reasons, not least of which is the fact that they play in America's oldest ballpark in baseball - a fitting icon for the oldest city in the country.
The team hasn't won a World Series since 1918, a legacy exacerbated by Gotham (and the Yankees) looming just four hours to the south.
"If Boston was the city of the 19th century, New York was the city of the 20th, and there are all sorts of economic and social rivalries mixed in," says Gleen Stout, author of "Red Sox Century."
The team's losing streak, say historians, has somehow become a means by which fans relive the Puritan tradition of always seeking salvation, while still finding familiarity and masochistic comfort in the status of the eternally doomed.
"It's most interesting when they lose," says Mr. Stout. "Since loss has been such a part of their experience, when a fan first experiences a loss that seems on par with losses of the past, that's sort of the membership card."
Even at the holy Fenway, Boston's contradictions are stark. A soda costs $4. Tickets are the priciest in baseball. Games have become an affair for suburban families and fat-cat professionals. The devotion of working-class fans made Red Sox nation what it is - but along with the rest of the city, that could easily change.
What seems eternal, however, is the city's political bent. Neighborhoods are split into hundreds of fiefdoms, allowing local powerbrokers to concentrate loyalty.
With all of these pols fighting for a slice of the political pie, and their deputies hungry for patronage and advancement, it's fertile ground for the rivalries and turf battles that endure.
That's the Tip O'Neil "all politics is local" kind of maneuvering that can hoist a man like Menino to a seat of enormous power.
And then there are the wonks and policymakers - the graduates of Harvard's Kennedy School of Government who prefer reading a policy paper to pressing flesh. That's the Michael Dukakis "cleaning up government" sort of politics that gives Massachusetts its reputation as a bastion of liberalism.
The two sides of the party, one parochial, the other intellectual, are simply Boston's two-sided character reflected in the public square.
"We are a one-party, two-ideology city," says Michael Goldman, a Democratic political strategist.
Both philosophies have their own flaws. The Big Dig, which had equal amounts patronage and pie-in-the-sky planning, is example enough.
Still, almost like a Boston version of checks-and-balances, the city's political dynamic has pushed it forward to a position of enviable prominence.
The Big Dig and new Greenway clearly mark another opportunity for advancement. Industrial Boston is coming down, and the New Boston is going up.
That will at least mean that residents can walk to the harbor without having to navigate around a fleet of traffic. They'll also see their city as it was, at leat to a degree, almost 400 years ago.
Boston will reconnect with its past. What it does with its future is an answer yet unbuilt.