But the city's conservative tendencies shouldn't automatically be dismissed. For much of its history, Philadelphia has maintained a healthy resistance to the fashions of the moment and a respect for how buildings are crafted. Even when the city was rolling in the smokestack wealth of railroads and coal, it rarely went in for the flamboyant - the exception being its fling with Victorian wildman Frank Furness. Yet it is a place of undeniable charm and livability.
Unlike big, brash New York and Chicago, Philadelphia remains a compendium of small delights - of 16-foot-wide rowhouses and Furness castles compressed onto corner lots, as wondrous as a Fabergé egg. The trick for Philadelphia today is to hang onto those core traditions (and its traditional core) while remaining a vigorous participant in the modern world.
If any architects are capable of a new take on the Philadelphia jewelbox, it is, ironically, the Manhattan-based firm of Tod Williams and Billie Tsien. The husband-and-wife team fashions thoroughly modern buildings with the nubby texture of something artisanal. In an era when celebrity architects jet from one job site to the next, Williams and Tsien are known for working on one project at a time.
Their last "big" project was the American Folk Art Museum in New York, built on a 40-by-100-foot lot. Now they've moved up to designing a bioengineering school for the University of Pennsylvania on a 60-by-140-foot site on 33d Street, south of Walnut.
Construction has just started on the $42 million classroom and laboratory building, which will be called Skirkanich Hall. From the designs, it promises to be an exquisite work of architecture in the best Philadelphia tradition. The solid portion of the asymmetrical facade may remind some people of the Folk Art Museum, but the contrasting cascade of glass makes it friendlier and less brooding.
Although the six-story Skirkanich Hall is pure Philadelphia in its size and openness, the architects avoid the reflexive red-brick traditionalism found in far too many new designs here, especially those produced by out-of-town architects with a one-dimensional idea of Philadelphia.
Skirkanich's exterior walls will still be faced in brick - and red brick at that. But the redness will be camouflaged by a mottled, hand-painted green glaze intended to shimmer with a spectrum of iridescent colors; only the barest traces of Philadelphia's red-brick past will peek through. It may not sound like a big deal, but the departure from standard red is almost a radical act on a campus where some recent buildings look as if they were shaped for Ben Franklin.
Williams and Tsien have made such handcrafted materials their signature. They approach architecture as if they were village weavers huddled over wooden carpet looms. Their custom materials highlight the variations, imperfections and uniqueness of the human hand. Assembly-line bricks, like those used at Penn's Huntsman Hall, just can't convey such rich complexity.
The facade of the Folk Art Museum was similarly handmade - from stock metal panels. The architects had those panels oxidized to bring out the material's earthy qualities and then laid them out on the ground to compose the best arrangement of color. Like Furness, who loved to fashion gargoyles and flowers from steel parts, Williams and Tsien transformed a mass-produced material into a handcrafted one.
At Skirkanich Hall, the architects take this artisanal artifice a step further. The roughly glazed bricks will play against the sleek industrial perfection of the facade's glass planes. While the bricks angle upward, the glass steps down in four large, overlapping plates - creating a cleft at the roofline that emphasizes the materials' irreconcilable differences. Step into the escalator lobby of the former PSFS building if you want to see a similarly sophisticated composition strategy.
During a recent guest lecture at Penn, Tsien described the division of design duties at her firm. Williams tends to organize the building's spaces, while Tsien focuses on the surface textures. But both see their buildings as intricate puzzle boxes that "don't reveal themselves right away. "
At the Folk Art Museum, you pass through the dark, light-absorbing facade into the jolting brightness of its sunlit galleries. Those galleries - really, a circulation system posing as a building - force visitors up an Escher-like complex of staircases. Skirkanich Hall will have a similar switchback arrangement of stairs.
Don't worry that engineering students will have to leave gingerbread crumbs (homemade, of course) to find their way back. Corridor windows will overlook a small, serene courtyard park, orienting the building's users. That two-tiered park, which is also a puzzle box, will be open to the public, accessed through a discreet outdoor passage.
This isn't the first time that the engineering school has veered from Penn's recent obsession with creating a fantasy atmosphere of Ivy League traditionalism. Last year saw the opening of Levine Hall, which was sheathed in a Mondrian-like grid of high-performance glass by the local firm of Kieran Timberlake. Skirkanich Hall effectively completes a networked quadrangle of buildings, which are all organized around the courtyard.
The school's dean, Eduardo Glandt, believes an engineering school must look modern, especially the one where the first digital computer - ENIAC - was invented in 1946. "We are the keepers of technology on this campus," he said. And that's a tradition, too.
Contact architecture critic Inga Saffron at 215-854-2213 or email@example.com.