It makes sense that the consumerist boom that followed World War II would produce some great retail architecture. If you travel Center City's shopping streets, you can still see a few of the exuberant storefronts that emerged in the '50s and '60s, before shopping migrated to the suburban malls.

One of the best examples is a shimmering black-and-white facade at 12th and Chestnut that stands out from its traditional neighbors. The building itself dates from 1909, but in 1962, Colonial Federal Savings Bank commissioned a makeover from architect Lee Casaccio. With a name like Colonial Federal, you might expect a staid design with red brick and shutters. Instead, Casaccio produced a modernist gem with almost pop-art sensibility.

Casaccio's composition is a high-wire balancing act. The narrow building is unusually tall and gangly, and he accentuates its odd proportions by dividing the facade into two unequal parts. The upper stories are covered in polished black stone, while the ground floor is clear glass. He also recessed the bank's shop windows, forming a contrasting void.

He didn't stop there. The glossy black stone is separated from the clear glass by a rippling white concrete canopy, an unusual bit of space-age Googie sculpture for Philadelphia. The concrete canopy continues right into the building, where it forms a barrel-vaulted ceiling. It also shapes the shop windows into four arched sections. Casaccio wraps it all up by outlining the facade with a steel band.

Perhaps Casaccio made the facade so top-heavy because he needed to camouflage the old windows on the upper floors. That large flat expanse would have been terribly boring had he not tufted the panels with stainless steel discs, which he called thumbtacks. The smooth surface is further enlivened by the reflections of the traditional windows across the street.

The black stone provided Casaccio with a neutral canvas for Colonial's neon sign, originally rendered in a loopy, lighthearted script. Some years ago, Colonial was replaced by the Philadelphia Federal Credit Union. A bland, printed sign now stands in its place, but the dramatic tension of Casaccio's composition remains undiminished.