The two-block expansion zone next to the Convention Center now resembles parts of Baghdad and Kabul. The ripped concrete openings of old loft buildings hang slack, like the mouths of the dead. But we know we're safe in Philadelphia because a dignified row of distinctly American commercial buildings still marks the site's edge along North Broad Street.

How long those early-20th-century structures will continue to give us our bearings is anybody's guess. The Pennsylvania Convention Center Authority and its minions have been working overtime to get that block between Arch and Cherry Streets demolished, even though the agency signed a contract in 2004 promising to preserve the three buildings and incorporate them into the center's Broad Street expansion.

In September, it looked like the authority was trying to pull a fast one on the Pennsylvania Historical and Museum Commission, which handled the preservation agreement. The Convention Center claimed that the two middle buildings, which originally served as the headquarters of Philadelphia Life Insurance Co., were unsound, and that city safety inspectors insisted they come down. The historical commission was set to acquiesce until it realized it wasn't getting the full story.

The unlikely hero in this is Wayne Spilove, who leveled a different historic block (at 16th and Sansom Streets) and now, through the miracle of Philadelphia politics, is chairman of the state historical commission. It was Spilove who encouraged his staff to take a second look at the convention center authority's request, said John Gallery, who heads the watchdog Preservation Alliance.

When they did, the staffers saw that the authority's engineering report was far from sufficient, said commission director Barbara Franco. Last Friday, her staff ordered an independent engineering inspection to assess the condition of the two threatened buildings. The result will determine their fate.

Franco, who was interviewed by telephone while a state information officer monitored our conversation, acknowledged that her agency nearly rushed to judgment in September. "There was a lot of confusion about the [city] inspection and what it meant," she said. "It was conveyed to us in one way, when it might have been conveyed in another. . . . So we said we need more information."

There's something else the convention center authority hasn't told Franco and her staff.

At the same time it was trying to wiggle out of its commitment to preserve the two conjoined buildings, the authority was also trying to sell the properties back to their owner, according to the owner's attorney, Herbert Bass. In August, he said, they made an offer "to revest the title."

The sell-back offer came as a big surprise, Bass explained, because the state had only just seized the two buildings, using eminent domain, to make way for the center's expansion. The two sides hadn't even come to terms on compensation, what's often called the "taking price."

Nevertheless, Bass' client, the estate of Meyers Parking, was excited. Bass believes those two little buildings will become highly valuable once the Convention Center's front door moves to Broad Street. They'd make a perfect spot for a restaurant, he suggested. A Center City developer has already inquired about buying the pair, along with the adjacent neoclassical tower, which is also owned by the Meyers Parking estate and not threatened.

But here's the Catch-22: How can Bass negotiate a purchase price for the two connected buildings when he still doesn't know what the state will pay his client for taking them? It can take years to sort out fair market value in an eminent-domain case.

And here's another question: Why does the convention center authority prefer to demolish protected historic buildings when it can sell them, make some money, and create an amenity that will serve future conventioneers?

To answer that question, you have to know some local history. Enlarging the Convention Center has been one of Gov. Rendell's pet projects ever since it was floated in 1997. Now that the $700 million enterprise is finally beginning, officials don't want anything to stand in its way - or cause the already huge price tag to balloon further.

Unfortunately, for some state officials, this block of historic buildings is squarely in the way. Under the preservation agreement, the Convention Center is supposed to chop off the back half of the conjoined buildings and knit them into the exhibition hall. No doubt it would be simpler to get them out of the picture.

But there's a good reason this stretch of Broad Street was singled out to be saved. Located just north of City Hall, its neoclassical buildings are hardly changed from their heyday, when Philadelphia's financial titans wanted to be close to the center of power. Other buildings targeted by the center's expansion were also historical, but only this ensemble survived in a way that allows us to visualize the city's development.

There was one significant change on the block, yet it makes it more interesting. In 1962, Philadelphia Life hired renowned architect Romaldo Giurgola to build an addition to its townhouse-sized Beaux Arts headquarters. He responded with a two-window-wide modernist masterpiece. It's those conjoined buildings that the Convention Center wants to raze, along with the former Odd Fellows Hall on the corner of Cherry Street.

History never stops in Philadelphia. It's worth pointing out that the first person to call attention to Giurgola's gem was Robert A.M. Stern, then a young architect and critic. He was inspired by the way Giurgola, of Mitchell Giurgola Architects, had reconciled the modernist aesthetic with the traditional city streetscape. Until then, most modernist buildings were stand-alone affairs, like the nearby Municipal Services Building. Giurgola's addition succeeded as both an independent work of architecture and a part of the ensemble.

Now, 45 years later, Stern is completing his first major Philadelphia building, the Comcast Tower. It, too, is a modernist building that reaches out to its neighbors, as well as a nice coda to a small bit of architectural history.

But that's not the only reason to keep this venerable block intact. The Convention Center's bland glass facade, by Thompson Ventulett, is a perfect example of modernism gone wrong. It needs Giurgola and his comrades to keep North Broad Street from becoming a more boring place.

Inga Saffron blogs about Philadelphia architecture at http://go.philly.com/skyline.

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Contact architecture critic Inga Saffron at 215-854-2213 or isaffron@phillynews.com.