On Thursday, the city will formally inaugurate a new urban core on a 61-acre, undeveloped parcel of land — a project that some experts say is unprecedented in city planning. Called Union Park, its supporters hope it will revive the historic downtown just to the east, where the region’s courthouses, government offices and oldest casinos are clustered.

More than $6 billion in mostly private money has been announced for five ambitious projects: an Alzheimer’s research center, designed by Frank Gehry; a 60-story international center for jewelry trading; a hotel by the celebrity chef Charlie Palmer; a casino-resort; thousands of residential units and square feet of office space, and, as its centerpiece, a $360 million performing arts center.

Construction on the rippled Gehry building and utility lines is under way on this former brownfield, once a chemical dumping ground for the Union Pacific Railroad.

“It’s quite unusual that there’s a big swath of downtown ground just sitting there without having to go through a whole rigmarole to acquire," said Bill Hudnut, a senior fellow at the Urban Land Institute in Washington. Mr. Hudnut, the former mayor of Indianapolis, recalled that acquiring just three blocks of that city “involved some legal fights and eminent domain, the demolition of buildings, numerous deals with numerous owners." In Las Vegas, he added, “they’re just building new stuff."

It is an approach recommended to the mayor of Las Vegas, Oscar Goodman, a criminal defense lawyer famed for defending mafia figures, by major developers brought in to tutor him in redevelopment after his election in 1999. The mayor, who admits he ran “almost as a game" to win, said he quickly realized that reversing the downtown area’s decline could become his most important legacy. (Downtown Las Vegas is immediately north of the Strip.)

“They all told me I couldn’t do anything because I didn’t have what I needed," which was land, recalled Mr. Goodman, now in his third and final term. “I despaired. Then I looked out my window and saw this fallow 61 acres of brownfield." The city acquired it by swapping other land with the holding company that owned the parcel. But it would take five years and several failed deals with developers before the city signed with Newland Communities to manage and design the site.

In the meantime, the city’s acquisition spurred other developers to snap up vacant land nearby. Union Park is now surrounded by an outlet mall and 3 of 10 buildings planned for the $3 billion World Market Center, a furniture-industry exposition space. The city’s plans “created the credibility of a Las Vegas that’s open for business outside of the Strip," said Robert J. Maricich, chief executive and president of World Market Center.

But the national economic downturn may play a role in how soon all of Union Park is realized. Already, the opening date for the $700 million World Jewelry Center has been pushed back one year, and questions abound as to whether the more than 3,000 residential units planned to be built will sell in a state with one of the highest foreclosure rates in the United States.

“There’s no question that the Union Park property is going be developed," said Matt Ward, editor of the weekly Las Vegas Business Press. “The question is whether some of these projects that were supposed to break ground this year will do so. We’re mainly talking about delays, I think. Are you going to see business leaders in town talking openly about that? Probably not."

Mr. Goodman has brought his boisterous personality and decades of friendships in the community to bear, persuading the region’s top liquor distributor, Larry Ruvo, to build the Lou Ruvo Brain Institute. The research center, named for Mr. Ruvo’s father, who died of Alzheimer’s disease, is a partnership with the University of Nevada School of Medicine.

The linchpin, though, is the Smith Center for the Performing Arts, Las Vegas’s first stab at a Lincoln Center-style facility that can be home for ballet and philharmonic companies. It will break ground in August.

“We don’t have a cultural hub right now," said Rita Brandin, the vice president and development director for Newland. “This provides that community gathering place."

Union Park does have skeptics, including Dave Hickey, culture critic for Vanity Fair, who is baffled by how the development will interconnect with the older downtown area and help in its resurgence. Mr. Hickey’s wife, Libby Lumpkin, is executive director of the Las Vegas Art Museum, and Mr. Hickey noted that Ms. Lumpkin rejected efforts to move that museum to Union Park.

“The idea is that they’re going to put in these public buildings and this is going to make a respectful downtown for Las Vegas without all the glitz and glamour, I guess, but I think it’ll be a ghost town," Mr. Hickey said. “I don’t see how the comings and goings will be facilitated. And those open spaces that landscape architects so love are not really conducive to the desert climate."

It also leaves the question of whether the city is abandoning the historic downtown, where all of Las Vegas was born 100 years ago.

Defenders like Ms. Brandin counter: “We’ve got an existing downtown. This is an urban core. It’s complementary."

And Mr. Goodman said the Union Park effort had helped kick off a decade of redevelopment in the older downtown region, which he expects to connect to Union Park via pedestrian bridges over the railroad tracks that run along the site’s eastern edge. Several casinos have new owners spending millions to upgrade, a bar district is starting to blossom and an old post office is being restored for use as a museum focused on mafia history, complete with interactive wiretapping exhibits. Most important, the mayor noted, are the half-dozen condominium towers nearing completion there.

“They wouldn’t have given you a plugged nickel eight years ago that there would ever be a high-rise residential building in downtown Las Vegas," Mr. Goodman said with a laugh. “It was unheard of."

And Union Park is now desirable enough to be a bargaining chip. Next month, the City Council is expected to finalize a plan in which a developer will build a new $150 million City Hall in the older downtown area in exchange for a parcel in Union Park where a casino-hotel can be built.

Still, the enduring down-at-the-heels reputation of the old downtown was a factor in Mr. Palmer’s decision to build in Union Park instead of the old downtown. “I call it the new Las Vegas," said Richard Femenella, chief financial officer of the Charlie Palmer Group. “They say they’re revitalizing downtown, but truthfully, everything west of the railroad tracks is all brand new. It was dirt."

Whether the old downtown is left behind is a concern of Linda Lera-Randle El, an activist for homeless people, who said that none of the residential units in Union Park were designated as affordable housing and that she worried that homeless people who squat on the vacant land would be displaced.

Not all of the mayor’s dreams have come to fruition. Several attempts to get a developer to build a sports arena, first at Union Park and then elsewhere, appear to have stalled. Mr. Goodman aggressively courted the Cleveland Clinic to take up residence, only to have the respected hospital pass. But the results of Union Park nonetheless stand to rewrite the national impression of Mr. Goodman as a Vegas caricature given to outlandish acts like suggesting that graffiti artists be de-thumbed or running a seminar on making martinis.

"I don’t always agree with Oscar, but I do think that Union Park is going to make it," said a councilwoman, Lois Tarkanian, one of Mr. Goodman’s most vocal detractors.