The answer: Head down. That's where architect Frank Gehry and his firm went with the design for the museum's long-deliberated, now cautiously implemented master plan.
"What's amazing is [this project] is the antithesis of what the architects are best known for, which is more exterior exuberance," Gail Harrity, museum president and chief operating officer, said on a recent facility tour, alluding to Gehry's flamboyant Guggenheim Museum in Bilbao, Spain, and swirly Disney Concert Hall in Los Angeles.
In Philadelphia, she said, the conundrum is: "How do you have that same transformative experience and punch and at the same time respect a historic landmark that's an icon for the city? This is one of the more complicated projects."
Most public comment on the museum's underground expansion plans has been about the idea of carving gallery space beneath the east terrace, facing the Benjamin Franklin Parkway.
But before that project could even be seriously considered, the art-handling facility around the corner had to be up and running. Its loading dock, with three truck bays, represents a gateway not simply for moving crates in and out but for much of the construction to come.
"It makes possible a lot of other things," museum director Timothy Rub said. "It is building the foundation, in this case expanding and renewing the underside of the museum.. . . And the underside of the museum, the lower parts, are key to renovation and expansion. We got a lot more square footage and moved some key pieces of the museum around, and that will free up some other parts."
Now, almost every day massive tractor-trailers pull off the Schuylkill Expressway and roll right up to the west side of the museum to digest castoffs and waste and disgorge packages and crates. Art handlers load trucks with paintings and sculptures, or off-load them into sealed, environmentally controlled holding spaces inside. In the expansive carpentry shop, display cases and even walls are cut, hammered, and framed out in preparation for special exhibitions.
There is a great deal of other backstage activity enabled by the art-handling facility.
A bank of pristine refrigerators holds food for cafeteria and restaurant. New drains, some plugged and awaiting use years down the road, have been installed. That means dumpsters have disappeared from the museum terrace, their purposes folded into Gehry's "loading dock."
Existing underground rooms have been renovated, fitted with new boilers, pipes, wiring, and exhaust fans serving half the museum. Soundproof studios are ready for video production or online education.
WiFi is museumwide, and areas available for educational programming have been expanded.
New state-of-the-art storage spaces now house the museum's holdings in decorative arts and many paintings not on view.
To do all this, the museum had to dismantle the sandstone wall below the west facade, dig out fill, and bring in a fleet of stonecutting machines to saw through its own 4-foot-thick foundation. Rock was scooped out and an entire new museum level created.
Gehry's firm, Gehry Partners, managed to locate the quarry that yielded the Roaring Run sandstone used for an exterior holding wall 80 years ago, and matched new blocks to cleaned older slabs for use around the truck-bay area.
When rebuilding the sandstone wall and the roadway above, the firm replicated Jacques Grebert's original 1920s stone pattern, creating a pristine path around the museum.
It even topped off the new truck bays with an eco-friendly green roof.
But as important as the new construction is to the museum's current functioning, equally important is what it opens up for the future. "It has been critically important," said Constance H. Williams, chair of the museum's board of trustees. "It makes everything else possible."
Just one example tells the tale.
The key museum entrance used to be through a great archway facing the Perelman Building and Kelly Drive; the arch opens onto a remarkable corridor running the building's entire width, straight to the river side. The tunnel, closed to the public in the late 1960s, has been used only for storage and loading since 1975.
Completion of the art-handling facility means that colonnaded corridor can be reopened, eventually providing direct public access to both the new galleries under the terrace and the existing building above. An empty elevator already exists from the corridor, and stairs blocked off by construction of the existing museum auditorium above will finally lead somewhere other than nowhere.
Completion of the art-handling facility also means that the next phase of construction and renovation must be carefully considered with an eye toward the museum's master plan, adopted eight years ago, and its newly minted strategic plan.
At its October board meeting, museum trustees decided that the most prudent way forward was to complete design development for renovation and reconstruction of a large chunk of existing spaces, and for the roughly 71,000 square feet of new gallery space envisioned beneath the east terrace. It also involves extensive system upgrades: fire suppression and wiring, windows, plumbing, and air control - name it and it probably dates from more than half a century ago. Rub called such renovations "desperately needed."
The design-development process, which has begun, he said, will take a bit more than a year. After that, trustees must consider how to proceed - wait, if the funding climate is tough, or plow right into a fund-raising and construction effort that could be far more difficult and disruptive than it was for the art-handling facility.
Museum officials said that when planning first began, it was thought that construction of new galleries beneath the east terrace would precede renovation and construction in the main building.
In the last two years, however, trustees and officials concluded that "we'd be better served working from the inside out," as Rub put it. That means terrace excavation would follow what Gehry has called "unclogging the arteries" of the main building.
"We've had a great deal of debate," said Williams. "We are planning for it in a methodical and incremental way. What we do will be exciting."
Museum officials won't yet discuss what various price tags might be. When the master plan was unveiled and renovation and expansion plans were announced in 2005, officials estimated it would take $500 million to bring the whole project home.
That included portions now completed - a new parking garage; opening the Perelman Building; refurbishing the Rodin Museum, and the main museum facades and roof; building the art-handling facility - in addition to the work that lies ahead.
Rub said recently that when all is said and done, about 60 percent of the total cost would be spent on renovations and improvements to existing space, and about 40 percent on new construction and expansion.
Getting to this point hasn't been easy. "There's been a great deal of debate," Williams said. "We have a number of trustees who will disagree in one way or another. We spent a year in discussion about the strategic plan.
"I think now everybody is excited and eager to get going. . . . I expect in four or five years to see something truly exciting. It will be transformative."
Contact Stephan Salisbury
at 215-854-5594, firstname.lastname@example.org, or @SPSalisbury on Twitter.