On a tour of Philly’s subterranean world, a simple question arises: Whom is our city for? | Mike Newall

The tour of subterranean Philly had already asked us to step back into the trolley-clogged Market Street of the early 1900s; wound us through a nondescript El stop once dubbed “the greatest subway station in the world"; positioned us on Arch Street above the ghost tunnels, the untouched corridors of a never-finished underground railway.

Our guide, Jenna Horton, had conjured visions of a Philadelphia transit system that actually spanned the city — one with miles more of subway and elevated lines, spurs and outgrowths from the Market-Frankford El and the Broad Street Line that never came to be.

Now we were underground again, in the closed Gallery, the latest of Philly’s subterranean spaces to undergo a radical transformation, with nothing left to do but blast DJ Jazzy Jeff and the Fresh Prince.

“We’re heading downtown to the Gallery mall,” sang the bards of West Philadelphia.

For Horton, an actress and tour guide for Hidden City Philadelphia, the story of the Gallery is a microcosm of Philadelphia’s weird, sprawling underground world. It was marketed as a luxury mall but became celebrated as one of the few diverse spaces in Center City, a touchstone for the black community that middle-class whites sniffed at. Now it’s aiming for luxury again, with a few hiccups along the way.

In short, it was built for one thing, became another, shaped the city along the way, and is now, naturally, being rebranded.

In its way, the extremely popular “Subterranean Philly: What Lies Beneath” tour is a story of how these underground spaces embody the biggest question facing Philadelphia today: Whom is this city for?

It’s a story of how underground transit shaped the city — but also of all that wasn’t built. About opportunities and visionary plans laid to waste by corruption and pure Philadelphia hackery, and how we’re still grappling with those decisions.

“It’s a story of what did happen and what didn’t happen,” said Pete Woodall, Hidden City’s project director and the tour’s author. “We had all these plans, and many never came to fruition. So we ended up with fewer subway lines than we might have — and a different city than we might have.”

Take the vision of Rudolf Blankenberg, a reform mayor known as “the Dutch Cleanser,” who won an upset against the corrupt Republican machine in 1912. The Cleanser and his transit director, A. Merritt Taylor, planned a system that looped around central Philadelphia and sped out into the neighborhoods — with spurs shooting along Roosevelt Boulevard, into Germantown, down Passyunk Avenue, and out to the Benjamin Franklin Parkway and even Roxborough.

None of this ever happened, thanks to the machine politics that still plague our city. Money set aside for the subway was frittered away — in part to cover how much money Republicans swindled out of the city’s Sesquicentennial celebration fund, possibly the most Philadelphia way to celebrate a birthday.

“It never came to be, and we still deal with that,” Horton said. Imagine a city with even 50 miles of subway tracks rather than 19 — and how that would have left neighborhoods less isolated, their residents with more ways to get to a job or get around. A city of neighborhoods still, but one that would have been more connected.

The tour wheeled through places of untapped potential like the concrete desert of the south concourse under Broad, a vastness most easily accessed at the Walnut-Locust subway stop. Kids now whip through its emptiness on low bikes.

Horton had her own suggestion for its revitalization: “Make it a shrine to Gritty. They’ll have no problems getting people down here.”

Under City Hall, she offered this tidbit: When engineers dug below it in 1915 to build the Broad Street Line, they realized to their horror that the building had no solid foundation. Just loose rock and gravel — perhaps too apt a metaphor.

The tour crystalized at the Gallery. At previous stops, Horton had said she wanted to collapse time — to flip the pages from the booming turn of the century to the grime of the `70s, and to now. Here in the Gallery, we’re seeing change in real time.

“We will get to see whether it is successful. Who is it for? Who does it serve?” she said. “And will we be able, in live time, to witness that?”