Some contend that the homeless population will put off potential tourists. Others say there's little the city can do to force people to move to other locations or to get off the streets. The problem, it seems, is at a stalemate.
"We have to find a reasonable balance between the kinds of things that go on behalf of the homeless and the ability of the city to market this great asset," Greenberger said.
More than 100 people cluster along the Parkway most evenings, although many of them lately have camped with occupiers at City Hall. Outreach workers have approached most of them about moving into shelters.
"We can't stop asking. Someone can be homeless for a long period of time, and you get them at that right moment and they're tired of living this way," said Dainette Mintz, director of the city's Office of Supportive Housing. "But we also can't force people off the street."
Mintz doesn't believe the homeless will deter the Parkway's growth. The bigger issue, she said, is a lack of housing.
"This ratchets up the need that we address the housing need of the population," she said.
Homelessness in general is a growing problem because of the economy, said Amy Burns, vice president of development for Project HOME, a nonprofit that serves the homeless. On any given night, 4,000 people are homeless in Philadelphia, with about 600 of them sleeping on the streets. Center City is attractive to the homeless for the same reasons it is to visitors - because it's populated, generally safe and often well-lit.
Monsignor Arthur Rodgers, of the Cathedral of Ss. Peter and Paul on 18th Street, said it's common for the homeless to sleep on the church's steps or to use the church's restrooms. Some visitors find that intimidating.
"People tell us, 'I'm so scared trying to walk down this last block,' " Rodgers said. "So many of these [homeless] people are absolutely harmless, but people don't know that, and they're afraid. It's causing a bit of a fear element along the Parkway."
The problem is intensified, he said, by well-meaning organizations that come to the Parkway to offer food to the homeless without offering opportunities for shelter or hygienic facilities.
"They have no place to have their meal or to take care of themselves after their meal," Rodgers said. "It's a very sad situation."
Paul Levy, chief executive of the Center City District, echoed Rodgers' assertion that the feeding programs were having a negative effect.
"Every service provider and outreach team will always say the best thing to do is not to feed in isolation but to connect it to services," Levy said. "Food is often a bridge that gets people into a conversation to accept help."
Mintz said the city is trying to identify an alternative outdoor space, one with proper facilities, for the feeding programs to use.
"There aren't a lot of takers who are willing to let us use their space for that purpose," she said.
Meryl Levitz, president and chief executive of the Greater Philadelphia Tourism Marketing Corp., said the new development will help the Parkway emerge as a new space despite the homeless - "just like Franklin Square did."
Before its development, Franklin Square Park at 6th and Arch streets was a weed-filled expanse that housed dozens of homeless people.
Franklin Square worked with organizations like Project HOME to help some park residents find alternative housing. Others moved on their own. In part, the park became less attractive to homeless because of the many people, including children, who filled it during daylight hours.
At night, a 24-hour security patrol maintains the area with a 1 a.m. curfew.
"Everyone doubted they'd be able to keep the square intended as a safe, nonthreatening place, but they've been able to do it," Levitz said.
When her organization surveys tourists about the city's least attractive aspects, the lack of parking is often cited as No. 1. But there are concerns about the homeless, especially panhandlers.
"When people are on vacation, they expect everything to be peachy," Levitz said. "When they see something that's dissident or troubling in such a beautiful place . . . if you're from a small town and you've never come across that, you will be put off."