The original proposal for honoring Independence Hall called for tearing down just a single block of buildings on Chestnut Street and creating a modest plaza where people could gather to celebrate the nation's founding. In the end, the city went on an urban-renewal spree in the late 1950s that leveled the better part of nine blocks between Chestnut and Race Streets. The intent was to create a Philadelphia version of the Washington mall. Instead, we got a dull linear park lined with even duller office buildings.

The majority have not improved with age, but a couple of designs are worth a second look as examples of Heroic (aka, Brutalist) architecture from the 1960s and '70s. Pietro Belluschi's Rohm & Haas Building on Sixth Street is the obvious standout. But lately, I also find myself admiring an unassuming 12-story office tower at Fourth and Market for its shapely, precast concrete windows and the two plazas notched into its corners.

Though most offices today are commissioned at the request of a single large tenant, the boxy tower was built as a speculative project by a North Jersey developer Philip Kalker. He had been courted by the city, which was eager to fill up the acres it had cleared for urban renewal. By the time the building was finished in 1970, Kalker had managed to lease a big chunk of office space to the Continental Insurance Co. and so "The Continental Building" was incised into the concrete facade.

The design is really a suburban product inserted into an urban setting. But considering the Continental cost all of $6 million, the little tower packs in a surprising amount of style. The facade is a repetitive grid of square windows sunk deeply into sculpted, precast window frames. The angled frames capture the sun as it passes overhead, washing the facade in a fascinating play of shadows. Now that slick glass is the official uniform of our modern office towers, it's a pleasure to experience a building with a little texture.

The tower, which was recently sold to MRP Realty and renamed 400 Market, was designed by Berger & Caltabiano, a New York firm that had done a lot of developer work. I managed to track down Burton W. Berger, now 86, and he told me he had been instructed to come up with a simple, repeatable, low-cost facade system that could be quickly installed. To relieve the building's boxy form, which was dictated by the dimensions of the Bourse next door, they cut plazas into the northeast and southwest corners. Because the project was subject to the Redevelopment Authority's Percent for Art program, the plazas became the pedestal for a sculpture designed by Constantino Nivolo. Responding to the facade's square grid, Nivola created a square female form using his signature sand-casting technique. It is a handsome piece, but the title tells you everything you need to know about gender biases of the late Mad Men era: It's called Dedicated to the American Secretary.

The plazas also provided entrances for retailers, but, unfortunately, they also take the pedestrian activity off the street. The design completely wastes the building's prime corner at Fourth and Market by elevating the retail to plaza level. Such disregard for urban streetscapes was typical of the time. As stylish and skilled as the Berger & Caltabiano facade is, the building is still a product of a period when cities were leveling whole blocks in the name of progress.