Pity poor Market East. Always a bridesmaid, never a bride.

Since the demise of the great department stores in the second half of the 20th century, there have been multiple attempts to revive its former grandeur. Beginning with the suburban-style Gallery in 1978 and the more recent attempt to rebrand it as the Fashion District, we have been bequeathed a largely chameleonic urban streetscape adorned with garish neon signage.

This wide primary boulevard first sketched by William Penn and his surveyor Thomas Holme in 1682 should be the crown jewel of Philadelphia shopping streets, like Fifth Avenue in New York, Oxford Street in London, and Michigan Avenue in Chicago. All these examples have one thing in common - a rich, varied, nuanced, mixed-use street life built over time - one that envelops and welcomes the pedestrian and does not overwhelm her.

That is the not-so-secret ingredient to great urbanism.

Jane Jacobs, the astute urban observer of the destruction of post-World War II American urbanism, noted, "The ballet of the good city sidewalk never repeats itself from place to place, and in any one place is always replete with new improvisations."

Jacobs used this metaphor as a glaring contrast to the destructive urban design elements of the postwar era such as inner-city urban highways that destroyed the intimacy of the urban streetscape and ripped communities, largely of color, apart.

We now have a proposal to build an arena for the Philadelphia 76ers on East Market Street in the place of a part of the old Gallery.

The old Gallery failed for many reasons, not the least of which was its soul-deadening endless street facade with minimal entrances to the interior mall to break the monotony of its hulking presence. It was like sucking all the air out of a balloon. Street life just collapsed.

It is true that the proposed site for the arena sits on the mother lode of all public transit alongside the Market-Frankford El and the Center City Commuter Connection for Regional Rail. This is a good thing.

What is worrisome is the urban design. The Romans built their arenas outside the city walls for a good reason - they were simply too big and monumental to be integrated into the cityscape.

We've learned a lot about creating good mixed-use development over the last couple of decades as we've sought to redress the sins of the postwar redevelopment era and rebuild our cities for people rather than cars. We have yet to come up with a good model of an inner-city arena.

By nature, these buildings are large, insular structures with a single purpose of accommodating large crowds only 41 days a year when the Sixers are home. That leaves a lot of downtime on the street. Think the Barclays Center in Brooklyn, one of the better examples of an urban arena with its transparent facade displaying the activity within.

The Sixers team includes a residential developer, and that is a good sign for the potential overbuild of housing atop the new arena. But what is most concerning is the street life. Can the Sixers pull off a successful transit-oriented mixed-use development that enhances the street? It's a tall order.

Madison Square Garden is an example of an urban design failure that clogs the vital center of what should be midtown Manhattan's glory. Yet, current attempts by the governor and the Empire State Development Corporation to revitalize the area are being met with stiff resistance from citizens hoping to maintain as much of the subtle urban fabric not destroyed in the 1960s when the arena was built.

These are cautionary tales for Philadelphia.

In our haste to embrace development for development's sake, we often throw urban design excellence out with the bathwater. This is a time to stand firm and work with the Sixers and their partners on a truly first-class urban stadium that celebrates Philadelphia street life and minimizes the stultifying potential of a hulking 90,000-square-foot arena.

We are a city with a great urban design lineage second to none.

Let's get this one right.

Harris M. Steinberg is the executive director of the Lindy Institute for Urban Innovation at Drexel University.