"Let me say very clearly," Mayor Nutter told an audience of several hundred assembled in an enormous tent at the construction site near 21st Street. "After a long journey, the Barnes is coming to Philadelphia. This is going to happen. . . . One of the greatest museums in the world will be right here."

The museum is scheduled to open in 2012.

Judge Marjorie O. Rendell, wife of Gov. Rendell, a longtime advocate of the move, told the assembled crowd that construction of the museum would "enhance the state's reputation" and transform Philadelphia into a "must destination" for visitors from around the world.

The governor, she said, had argued forcefully that the addition of the Barnes collection would go a long way toward realizing "the potential inherent in this collection of cultural institutions" along the Parkway.

Not everyone at the fenced-in future site of the Barnes, which has been in Lower Merion for more than 80 years, was pleased with the event. About 20 protesters stood on the Parkway and at the site entrance hoisting signs in opposition.

"Crime Scene Do Not Enter," said one. "Toxic Area Tax Dump Site," said another.

The demonstrators are among partisans engaged in a five-year losing battle that has sought to block the move, arguing it violates the trust indenture that created the foundation and eviscerates a unique institution.

Albert Barnes, a wealthy patent-medicine maker, conceived of the foundation as a school designed to teach students how to look at and understand art. He directed that the location of his collection - both on the walls of the Merion galleries and on the very site in Merion itself - not be altered in any way.

Barnes' art is widely considered one of the greatest private collections of Impressionist and early Modernist work ever assembled.

Barnes died in a 1951 automobile accident.

Years of costly litigation in the 1990s and restrictions Barnes placed on endowment investments sapped the financial stability of his foundation.

In 2004, Montgomery County Orphans Court ruled that a move to Philadelphia was the best alternative to maintain the foundation's fiscal viability.

According to foundation officials, the Philadelphia facility will cost about $150 million. In 2006, before architects were selected, a facility of $100 million was projected; at the time, an additional $50 million was planned for the endowment.

After that $150 million had been raised (May 2006), the Barnes board decided to seek an additional $50 million for its endowment, at which point the project became a $200 million effort.

Derek Gillman, Barnes president, said that the $150 million included all costs associated with the move to the new facility, not simply construction, and that the increase "doesn't seem immensely dramatic."

The foundation has raised "close to $160 million," he added, with some pledges not yet publicly announced.

"We are actually very confident we will meet the goal before too long," Gillman said. "We aren't going to stop fund-raising."

The size of the building, projected at 120,000 square feet in 2004, before architects were selected, is now about 93,000 square feet. The foundation will be making greater use of its site in Merion for storage and object conservation; a conservation lab already exists there. A lab for painting conservation is still planned for Philadelphia, however.

At the groundbreaking yesterday, Bernard C. Watson, Barnes board chair and an aggressive backer of the move, entered the grounds by walking past a line of protesters standing in a damp, chilly wind.

"Shame on you, Mr. Watson! Shame on you!" move opponent Robert Zaller called out.

Watson turned, without breaking stride. "Good morning," he said, and headed on into the tent.