For much of the last half-century, anyone who passed through Philadelphia's civic heart had to traverse at least one of three inhospitable islands encircling City Hall. The trio of granite-paved plazas - Dilworth, Municipal Services and JFK - were an unfortunate legacy of the 1960s, a time when such grandiose spaces were built as pedestals for buildings, rather than parks for people.

Neglected for decades, at least partly out of disdain for their harsh designs, the spaces have now become a priority with city officials. With the Convention Center about to establish a presence one block north of City Hall, all three are being targeted for major makeovers.

The changes under discussion have the potential to radically transform a governmental no-man's land into a big-city version of a town square. Dilworth and JFK (a.k.a. LOVE Park) would be made into softer, more parklike settings featuring lawns, cafes, and a skating rink. The forlorn plateau on the east side of the Municipal Services Building (officially, Reyburn Plaza) would be eliminated altogether and marketed as a hotel site.

In terms of ambition, the combined renovation effort could rival the recent overhaul of Independence Mall, a '60s-era project that was recast in a gentler, if imperfect, form. But more is at stake at this end of Center City because the plazas sit at the epicenter of Philadelphia's daily life: the juncture where the city's downtown office core, transit network, convention district, and an emerging residential neighborhood all come together.

The projects are moving at an unusually fast pace. Designs for the Dilworth project, which is being managed by the Center City District, will be submitted to the Art and Historical Commissions next month. Meanwhile, the Philadelphia Parking Authority just advertised for a design team to reconstruct JFK Plaza, and city planners have drawn up design guidelines for the project.

From the looks of the available designs, the proposed plaza improvements will almost certainly make it easier to navigate the area around City Hall. The real trick, however, will be to create spaces where people - residents and tourists alike - also want to linger.

Tourists already are on the city's mind. Next month, the Convention Center will complete a massive expansion that relocates its front door to Broad Street, just a block from City Hall's freshly scrubbed facade. At the same time, owners of several nearby condo buildings are clamoring for improvements that would enable the plazas to evolve into amenities like Rittenhouse and Washington Squares.

While there may be no magic formula for transforming the dreary plazas into beloved public parks, there is little disagreement about why these spaces failed in the first place.

For starters, there are too many in the same place. Conceived by legendary planner Edmund Bacon, and executed by Vincent Kling's firm, the trio were part of the grand scheme to create a downtown of the future, with offices and retail integrated into the underground transit system. In keeping with the values of the time, the plazas were arranged to set off views of new towers, like the modernist campanile Kling built to house city services.

In theory, the plazas should have been great places for downtown workers to lunch alfresco, but their high walls, multiple staircases and limited entry points made them challenging to access. Because people couldn't easily see into the plazas, they felt unsafe. As maintenance slipped, people were further put off. One reason that skateboarders were able to move en masse into JFK Plaza in the 1990s is that no other constituency claimed it.

Now the city has a chance at a real transformation. Because the parking authority needs to rebuild its crumbling, 810-car garage below JFK Plaza, it must raze the surface - obliterating the last traces of Bacon's vision, as well as the beloved skateboard course. Those losses will be worth it if the city can deliver a great park.

So far, the project is being managed in a professional, transparent way that suggests the hope is justified. Given the parking authority's $35 million renovation budget, there is no reason the city shouldn't be able to hire a first-rate landscape architect for the job by the late April deadline.

Still, not everything can be fixed. The high walls on the east side exist for a reason: to camouflage ventilation shafts for the garage. The Arch Street car ramps are also an impediment to entering the park from the north. But the city has floated an intriguing proposal to relocate those ramps to the west side of the Municipal Services plaza, under that plateau. Although costly, the switch would make it possible to restore a full sidewalk on Arch Street, for easy access to the park.

One concern, however, is that the planning guidelines impose constraints that could limit the designer's creativity. The diagonal axis with the parkway, the placement of Robert Indiana's LOVE sculpture, the round, Googie-style visitor center and the flower beds on the west side must all be retained.

The issues with Dilworth Plaza are more complex. Kling's original design, based on Rome's Piazza Navona, is more inviting and has moments of real beauty. Some in the city design community believe that its problems stem from poor maintenance, and argue it should be rehabbed rather than redesigned.

They're also upset that the new design, by Olin and KieranTimberlake, hasn't been subjected to the same level of public back-and-forth as a city-run project. Center City District President Paul Levy said he plans to present the $55 million design to neighborhood and design leaders later this month, but that's just days before the hearings at the Art and Historical Commissions.

Levy's vision for Dilworth is a clear reaction to the fussiness of Kling's 1976 design, with its excess of stairs, level changes and ornate balustrades. Olin's design calls for a simple flat surface, featuring a lawn at the south end, a cafe at the north, two transit headhouses and a programmable water feature. The advantage of the concept is that it could serve as a plain backdrop for any event, from a farmers' market to an orchestra concert.

While that makes sense, questions remain about the need for the two curving headhouses and an elaborate underground "transit room." They're meant to elevate access to the subways into a grand experience. But because most subway riders enter from the west side of 15th Street, it looks like these transit amenities are there for show - and to help attract federal transportation money for the project.

In many ways, the approach to redesigning the three plazas is an extreme reaction to their conception. In the '60s, Bacon imposed his single vision on the group. Now city planners are merely offering input for Dilworth and JFK Plaza. At least they still call the shots at the Municipal Services Building.

They've prepared conceptual drawings to show how a hotel could be placed on the plaza, and are weighing how to market the site to developers. The MSB tower was meant to stand in splendid isolation on the plaza, so there are potential design problems that will have to be overcome if another building is placed next door. But filling in that big void would do wonders to activate the dead frontage on Broad Street.

One of the sobering lessons to come out of the Independence Mall renovation is that original design sins are not easily overcome. Yet, the way things are going, two of the three plazas could be torn up for construction by late 2012. That doesn't allow much time to figure out how to repair a 50-year-old mistake.

Contact architecture critic Inga Saffron at 215-854-2213 or