If there is a cursed building site in Philadelphia, the grassy lot near 19th and Walnut is it. A small movie theater on the property went up in flames in 1994. Despite an enviable address overlooking Rittenhouse Square, bordered by some of the priciest real estate in the city, the one-acre parcel has defied development ever since.

That is not for want of trying. Every few years, a new owner would trot out a fresh proposal, only to be caught in the undertow of market downturns or buffeted by local preferences. At one point, Mayor Ed Rendell insisted the site was perfect for parking and tried to ram through a 500-car garage. An ambitious Irish developer later swooped in, paid a record $37 million for the land, and promised to bring in a celebrity designer. He went bust soon after.

In spite of this history of failure, the latest design for a 565-foot, mixed-used tower is worth taking seriously. Not only does the project from Southern Land Co. have the fewest negatives of any proposal to date, it has been enthusiastically endorsed by a coalition of high-powered neighbors. Political forces are lining up behind the project. This could be the one that breaks the curse.

Southern Land, it should be cautioned, tried to build there once before. A year ago, it released renderings showing a somewhat taller (600 feet), all-glass skyscraper hovering over Rittenhouse Square like a knife blade. Dazzling as it looked from afar, the design ran into trouble over its inability to fit in on the ground, and Southern Land's insistence on leveling a couple of historically certified buildings on the Sansom Street border.

The glass tower, designed by the Chicago firm SCB, also received the ultimate kiss of death in this town: It was deemed insufficiently "Philadelphian."

The new version released last month is very Philadelphian, which, sadly, is still a way of saying quiet, conservative, and familiar as a blue blazer. It is not a cynical fake, in the way that 10 Rittenhouse is, or a lifeless stack of residential units, in the manner of the Rittenhouse Claridge and the Savoy. It's just less ambitious than what this extraordinary site deserves.

The architects bear only part of the blame for the new, toned-down version of 1911 Walnut. After it appeared the project was going to be derailed by zoning and preservation issues, Southern Land agreed to work out a more palatable version with an ad hoc group of neighbors and consultants, including Cecil Baker, who sits on the city's Civic Design Review board and who often serves as the city's design conscience.

The coalition persuaded SCB, the same firm that gave us the St. James and the Murano, to ditch the all-glass facade and emphasize the horizontal floor slabs, effectively rooting the building in Philadelphia's brick-and-stone traditions. Given that blue-tinted glass skyscrapers are becoming a cliche, here and around the country, switching to a more tactile and textured material is appealing. SCB also slimmed down the tower substantially, from 180 to 135 feet on its east and west facades. That's all good.

The problem is that SCB doesn't do anything creative with these changes. It's more or less the same tower, just with less glass and none of the fancy vertical layering of the original design. Compared with the meaty and assertive concrete floor slabs at the Murano, which serve as the starting point for the whole design, these thin slabs come off as just an arbitrary choice.

The new version has a more classic skyscraper arrangement, with a base, shaft, and crown, but once again, SCB seems to be going through the motions to appease local tastes. The crown, created by an opaque glass screen around the ventilation equipment, mimics the penthouse setbacks on the adjacent Rittenhouse Plaza. Walnut Street's ground floor could be any batch of high-end but anonymous Philadelphia townhouses. Only the crisp, black-rimmed storefront bay at the eastern end demonstrates a bit of flair and real aesthetic conviction.

Of course, it's the small elements — the ones you can't see in the renderings — that could elevate the final design into a fine background building. SCB architect Clara Wineberg says her team is refining the profile of the floor slabs and the window trim. Luxury, these days, is in the details.

The coalition's real victories are on the ground. The group persuaded  Southern Land to eliminate a massive garage entrance on Sansom Street, dubbed a "parking court," and to  instead widen Moravian Street and use it to access the underground garage. The developer will also preserve two beloved historic buildings, the Rittenhouse Cafe and Warwick apartments.

Though a third historic property, the Oliver Bair Funeral Home, is unfortunately being sacrificed so the plan can work, what makes the loss tolerable is a remarkable gesture by Southern Land. Rather than keeping the pair of preserved buildings, it will donate them to Project HOME for affordable housing serving homeless people returning to the workforce. The developer is also providing $2 million to offset renovations, expected to cost around $13 million.

You might expect the neighborhood's affluent residents to object to such housing, but they ran with the idea. For people trying to live on minimum-wage salaries, the location can't be beat for its convenience and transit. And because Project HOME already manages an affordable apartment house on the block, it will be easy to absorb a few more units.

Between the two historic structures, the nonprofit hopes to carve out 35 additional studio apartments, roughly 10 percent of the total number of units in Southern Land's tower. Because the unique arrangement is not covered under the zoning code, the neighbors are working with Council President Darrell Clarke on an amendment that would allow Southern Land to claim a density bonus and reach its 565-foot goal for the tower.

For such a storied public space, one that functions as the city's common living room, it's ironic that Rittenhouse Square has rarely produced architectural greatness since the erection of its first high-rise, the beaux arts 1830 Rittenhouse Square, in 1913. Indeed, many of the towers that followed have been clunkers.

Southern Land's skyscraper — the last high-rise on the square — will almost certainly be better than that. But it will be up some other neighborhood to demonstrate that "Philadelphian" and 21st-century ambition are not mutually exclusive.