Skyscraper Height No Object?

When its exterior was completed last year, the 975-foot-tall Comcast Tower ended One Liberty Place's 20-year run as Philadelphia's tallest building. It seems unlikely that Comcast will be able to hold onto the city's height record for quite so long. Even as Comcast puts the finishing touches on its plaza and underground concourse, a group of developers is proposing an even taller tower - the 1,500-foot American Commerce Center. While it's a long-shot of a project - as I wrote in a story that ran Saturday - it signals that Philadelphia is entering the age of super-tall towers.

The project is being shopped around by Joseph Grasso's and Garrett Miller's Walnut Street Capital, which spent $30 million on the site. Some handicappers suspect they are in way over their heads. Unlike Liberty Property Trust and Brandywine, which are the only companies to actually build new offices in Philly in the past two decades, Walnut Street Capital has never put a shovel in the ground. Their ambitions for the American Commerce Center are very grand, considering. First there is a 1,200-foot office tower (topped by a 300-foot spire) that would include 1.3 million square feet of office space (same as Comcast). But there is also supposed be a second, 477-tall cubular donut that would house 300,000 square of retail in a five-level base and a hotel, located in the southern leg of that open rhomboid you see in the rendering. The architects, Kohn Pedersen Fox, of New York, envision three different plazas, which would host various cafes, a movie theater complex and the hotel ballrooms The dense array of activities could, theoretically, be a smaller Philly version of the shops at Time Warner's building. There's even space set aside for an upscale supermarket in the lower level, just like Time Warner's Whole Foods space.

The architects have done some clever things with the design, like hollowing out the lower structure to preserve some views for the Stirling on JFK Boulevard. The top level of the open rhomboid would have gardens and meeting rooms that can do double-duty as both a conference center for the office tenants and ballrooms for the hotel.

But it would be nice if KPF designers Eugene Kohn and William C. Louie had worked out the architecture beyond this schematic form. You would think they'd be a little embarrassed at stealing the idea for the crown from Daniel Libeskind's original pass at the Freedom Tower in Lower Manhattan (see image below). And while the architects say they haven't begun to work on the details of the facade, it's disheartening to see their starting point is the same bluish glass used at Le Petite Cira and half the new office buildings in New York. KPF, which designed cool, angular One Logan Square and the far-less-cool, Post-Modernist Two Logan , as well as the Mellon Bank Center, does seem to have a good recent track record of manipulating glass curtain walls to give them depth and shadow. Of course, most of their recent clients have been in places flush with money, like Shanghai and Kuala Lumpur. We haven't seen any Philly developers willing to spend money on the detailing necessary to make a glass facade more than a vertical ice rink.

My greatest concern, however, is the boxy mass of the tower. It appears to slam down hard on the ground at the corner of 19th and Arch Streets with no set backs and no grace notes. If you've walked around to the back side of the Comcast Tower, then you known how these sheer glass skyscrapers walls can easily become an urban cliff. Given that Ron Caplan, et al, are assembling land for yet another tower immediately to the west, on Arch Street between 19th and 20th, Philadelphia needs to plan now to avoid building a forbidding palisades of skyscraper walls. See my Friday column for more on that subject.