The owners of one of Boston's uglier buildings are trying to stop the renovation of one of its most beautiful.

Sadly enough, they may succeed.

The ugly building in question is Tremont-on-the-Common, a plain white-brick building that looks out onto Boston Common from its perch on Tremont Street. Built as low-income rental housing in the mid-1960s, it now is a condominium with 376 residential units. Its distinguishing architectural feature, if one can call it that, is that the first third of the building has no windows.

The beautiful building in question is the Opera House on Washington Street. Built in 1925 as a vaudeville house called the Keith Theater, it was designed by noted theater architect Thomas Lamb.

The Opera House - it got its name because it was for a while occupied by Sarah Caldwell's opera company - closed in 1991. Yet even after years of collecting dust and mildew, it is an amazing structure.

The building's entrance, only 22 feet wide or about the width of a Boston townhouse, presents an unassuming face to Washington Street. But walk through the front doors and another world unfolds.

The ceiling of the 2,500-seat theater soars eight stories overhead. In the gloom one sees elaborate frescos, tapestries, crystal chandeliers and carved marble and oak. The eerily empty seats still have decade-old programs from the theater's last presentation, a performance by New Age musician Yanni.

Preservationists have long viewed restoration of the Opera House as a kind of Holy Grail. Now that goal is within reach.

Texas-based Theatre Management Group is ready to break ground on a $25 million renovation that will not only restore the Opera House but will make it a venue for Broadway-style plays. For Boston's arts community, it marks a key step in the rebirth of a vibrant theater district.

There's only one problem. In order to accommodate Broadway plays, the theater needs to expand the depth of its stage from 28 feet (which was fine for vaudeville) to 45 feet. Doing so means pushing out the back of the theater and taking over part of Mason Street, which runs between the theater and Tremont-on-the-Common. The street, now 30 to 32 feet wide, would be narrowed to between 10 and 12 feet.

It's no great loss. This part of Mason Street is nothing more than a service alley for the condos, and has degenerated into a hideaway for drunks, a fact attested to by the empty bottles of Colt 45, Irish Rose and Listerine (Listerine!).

At first the condo owners seemed reasonable. They said they were concerned about safety and access. But as the review process has worn on, and as the police and fire departments both have given their approvals, the owners' complaints have become more specious.

For example, Tremont-on-the-Common now claims narrowing the street will prevent trash from being removed from the building. As it turns out, the city itself removes the trash. So has the condo bothered asking the city if it will no longer remove trash after the Opera House is renovated?

``It's not incumbent on us to call them,'' says John Trefethen, chair of the condo association.

Huh? The condo association has hired high-priced lawyers to block the expansion, it's threatening lawsuits that outsiders figure will cost it another $200,000, it paid consultants to ``prove'' trash couldn't be picked up - but it can't make a simple phone call?

So I called.

Turns out, it won't be a problem. The city removes trash in much more difficult circumstances. It will figure out a way for Tremont-on-the-Common. The Opera House's new owners have even offered to forklift trash out.

None of that seems to matter. Indeed, the condo association's motives are hard to fathom. It dismisses each solution to each objection. One is left with the feeling that the real issues are resistance to change, pique about the construction of nearby Millennium Place and a refusal to tolerate the slightest inconvenience.

The condo's objections, if they continue, mean the almost certain doom of the Opera House. The building will not be able to survive another winter. Roof leaks have infiltrated the plaster ceilings. The damage is accelerating, exponentially, says an outside engineering firm, which estimates that in another year the building will be incapable of being restored.

The Boston Redevelopment Authority is expected to make final approvals for the renovation in June, with construction commencing in August. But Trefethen says, ``We absolutely would sue.''

Any such suit might delay construction until it was too late.

And the condo association's response to the potential demise of the Opera House? Tough.

The moral of this story is not that public process is a bad thing. In many cases, it is only by thoroughly vetting concerns by abutters, preservationists, environmentalists, resident groups and others that high-quality projects get built.

But that isn't the case here. How tragic it would be if Yanni, a maker of what one critic called ``music for the bubble bath,'' were to be the last act to grace this magnificent structure.

Thomas M. Keane Jr. writes weekly for the Boston Herald. He's reachable at tomkeane@tomkeane.com.