By Pat Ciarrocchi

PHILADELPHIA (CBS) – Since the Philadelphia Museum of Art opened to the public in 1928, no one has ever undertaken a comprehensive renovation.

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Now, the museum plans to start with the electrical and mechanical systems and excavate the land underneath to create enormous new galleries.

But it’s also toying with the idea of changing the steps that made Rock famous.

“You actually have split the Art Museum here. You want people to look inside and see what’s going on,” explains the museum’s director Timothy Rub.

A look inside elaborate models, the centerpiece of the exhibit, reveals an unprecedented expansion plan.

“The first part, which we’re calling the core project…we’re going to take the auditorium out of the center of the building and build a new public space,” Rub says. “We’re calling it The Forum, which exists just below the Great Stair Hall.”

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From that point, the change is ambitious, with a timeline of at least 10 years. A new 55,000-square-foot gallery would be created “just below the Great Porch…that will be the entrance to the new galleries underneath the Terrace.”

The earth and rock underneath the East Terrace, which faces Center City, would be excavated down to the Kelly Drive-level to the famous steps.

“We are toying with the idea of changing the steps and perhaps introducing a window,” Rub says.

That would allow visitors to look out and look into the new gallery, but would make it very difficult to run up the stairs to victory.

“This is just an idea that we are putting out there now. It can go either way,” explains Rub.

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Rub also says the museum would hear reaction from the public and the Historic Commission before moving forward. The price tag on the first phase of the core project is $150 million.