"I went from moron to genius," Blumenfeld said.
Perception is everything in real estate, and in recent months, the view looking north on Broad Street has begun to change for the better.
Since the city dubbed a 3.5-mile stretch of Broad Street the Avenue of the Arts in 1993, most of the action has happened south of City Hall.
With the addition of the Kimmel Center for the Performing Arts and the Suzanne Roberts Theatre, South Broad has lived up to its reputation as the city's cultural heart.
The northern half of the arts district, from City Hall to Glenwood Avenue, has always been a harder sell. It's pockmarked with vacant lots, and the derelict Divine Lorraine Hotel at Ridge and Fairmount Avenues stands like a glaring symbol of blight.
But in the past year, major projects have opened, and more than $500 million in new development is planned for the stretch of North Broad from City Hall to Temple University.
The street, too, will get a $12 million face-lift this spring with landscaping and 29 pillars of light, stretching from Spring Garden to Norris Streets.
Among the projects under way:
The Pennsylvania Ballet is building a $17.5 million headquarters at Broad and Wood Streets that will include studios, a dance school, and offices.
As part of its 10-year capital plan, Temple is building a $147 million residence hall at Broad and Cecil B. Moore Avenue, and a $48 million expansion of the Pearson and McGonigle Halls sports complex. The university also has renovated a shuttered church on Broad into a performing arts center.
Developer Bart Blatstein of Tower Investments is moving ahead with two projects in the 400 block of North Broad Street: the conversion of a state office building into apartments, as well as a "mixed-use" development for the current headquarters of The Inquirer.
"North Broad Street is a sleeper," Blatstein said.
At the state office building, Blatstein is changing the space into 204 rental apartments. He also wants to build a second, 20-story tower and 60,000 square feet of retail space at the site.
Concerning the Inquirer property, which includes a parking garage and surface lot just west at 15th and Callowhill Streets, Blatstein said he could not discuss the project, saying only, "It will be a very large mixed-use development."
Philadelphia Media Network Inc., the owner of the newspapers, is in discussions about staying in the building.
"We're looking at a number of options in Philadelphia and New Jersey and among those options, we're looking at staying where we are," said Michael Kuritzkes, general counsel for Philadelphia Media.
At the groundbreaking for the Pennsylvania Ballet project, Mayor Nutter celebrated the change on North Broad.
Standing in a gutted brick garage that will become a dance studio, Nutter said, "Watch the transformation of North Broad. It's taking place right before your eyes."
When Nutter looks north from City Hall, he now sees the expanded $786 million Convention Center, which has a front door on Broad Street. It sits across the street from the new $7.5 million Lenfest Plaza, featuring the giant Painted Torch sculpture by Claes Oldenburg.
But Nutter also sees the graffiti-scarred Divine Lorraine, and it bothers him. The city, he said, is leaning on the owners - a development partnership including a Dutch company - to move on the project, which owes $676,692.04 in real estate taxes.
"We're trying to get the attention of the building owners before we take action ourselves," he said.
"If we can get moving on the Divine Lorraine," he added, "we will have reached the tipping point for North Broad."
As one of the early converts, Blumenfeld said the area is already there. He sees the Pennsylvania Ballet's decision, in particular, as "an affirmation" of the potential for the northern half of the Avenue of the Arts.
"I used to be here all by myself," Blumenfeld said. "All of a sudden, the big boys are showing up."
Blumenfeld has attracted three culinary talents to the renovated car dealership.
The first venue - the Vie catering hall - opened Saturday with the Pink Tie Ball for 650 patrons of Susan G. Komen for the Cure.
Joseph Volpe, owner of Vie, has invested $4 million in the site. With two catering halls in Northern Liberties, he said, he needed no convincing from Blumenfeld to move to North Broad.
The service bays and showroom have been converted into a ballroom with white columns and chandeliers, a dance floor, a stage, and four bars. Volpe said he has 75 weddings booked for the next year.
"The next big corridor," Volpe said, "it's here."
Next month, restaurant entrepreneur Stephen Starr will move in next to him with a casual seafood chowder house called Route 6. Early next year, Italian chef Marc Vetri will open the Alla Spina gastropub.
Vetri blazed a trail in the neighborhood five years ago by opening Osteria in Blumenfeld's first building at 640 N. Broad.
While the opening of the Convention Center expansion has added life to the area, he said the neighborhood was gradually evolving.
"It's a slow-moving process," Vetri said, "but it's been moving."
City Councilman Darrell L. Clarke, whose district includes sections of North Philadelphia, said the revitalization of North Broad was tangible and would be beneficial to all, even though most of the new investment is geared toward higher-income residents.
"There's no written rule that you can't have a level of diversity on North Broad Street," Clarke said. "The more investment on North Broad, the more the economic spin-off for the North Philadelphia community is enhanced."
Contact staff writer Jennifer Lin at 215-854-5659, email@example.com or @j_linq on Twitter.