This summer, Philadelphia’s SEPTA regional rail system — newly flush with state funding — took a 30-year lease with the city on the 3.5 miles of tunnels that run beneath the heart of downtown. Inspired by this news — and by John Updike’s 1956 New Yorker article “Rockefeller Center, Ho!,” which purported to chart a path from the Empire State Building to Rockefeller Center without ever setting foot on Fifth and Sixth avenues — I set out to navigate the city’s bowels from 18th and Market to 7th and the same.

Enter through the Mellon Center’s Philadelphia Sports Club at 18th Street. Descend the stairs at a rapid clip, politely declining membership offers from the imposingly athletic instructors. Revel in the climate-controlled air and enjoy the bubbling fountains in the studious quiet of an atrium before exiting into the vastness of Suburban Station, central HQ of the regional rail system.

Take a left and breach the basement of the tallest building in Philadelphia. The lower recesses of the Comcast tower are adorned with portraits of a diverse array of humans and carefully arranged bowls of fruits, all by students of the Studio Incamminati School for Contemporary Realist Art. “I really like the one called ‘Gossiping Puppets,’ says a security guard, cutting against the principal thrust of the collection, which tends towards tasteful nudes (mostly female). “It’s the eyes, like children’s eyes, like they’re having fun.” Stocked with Termini Brothers and Di Bruno Brothers branches, the Comcast market is home to satiated office workers and subtly expensive lunch options. Use the impossibly clean bathroom.

Upon exiting, resist the urge to enter the first of the approximately several hundred Dunkin’ Donuts that dot the concourse. Then consider the options. Walk straight (west) through the heart of Suburban Station, to the tune of the warbling robotic garble of SEPTA’s PA system? Or hook a right past the La Barberia barbershop to the tunnel less travelled? Being a hardier breed — especially after inhaling a Termini Brothers pastry — we tack south.

After turning the corner, we regret our decision. (Even the barbershop doesn’t look as friendly from this angle.) Before us rolls a seemingly interminable expanse of shoe-scuffed white tile. A briefly gaping portal to the left reveals a mail-sorting room, while the uninviting façade of the Turf Club — “Advance Wagering and Phone-Bet Deposits” — looms to the right. Although the warm electronic red of a bar sign welcomes us in, the doors are all locked despite the presence of an operational escalator on the other side of the glass and the quiet humming of its false invitation. Egress is impossible from this angle, a Center City District employee explains, because “someone hit the ATM machine” years ago and then beat a successful retreat through the tunnels with their illicit winnings.

Continuing down the hallway we pass a financial services office, a store promising “a dollar for everything,” a wig shop, Church’s Chicken and Nutty World, which is dubiously subtitled “Health Snacks” despite the abundance of rainbow-hued candies. This stretch leads past signs both inviting (“Cold Beer To Go”) and supplicating (“We Buy Gold”). Having abstained from the pleasures of yet another Dunkin’ Donuts, we leave the air conditioning and enter the sticky heart of the city’s transit system: 15th Street station under City Hall.

Follow the wail of a trumpet player and the rumbling growl of arriving subway trains — note a large Mennonite family deep in conversation with a voluble homeless man — and shoulder through the bursts of commuters exiting from the Broad Street and Market-Frankford lines. Cross to the shoe repair place and present a pair of cracked and faded loafers to the storekeeper, who clucks her tongue mournfully. Thoroughly chastened, we proceed to the adjoining tunnel on the southern side and enter the loneliest stretch of the trip.

All but the most intrepid of travelers will prefer the bustling street to this empty, moldering passage. Scurry through this grim stretch as quickly as dignity will allow, pausing only to admire the foolhardy bravado of the Ritz-Carlton. (The sign was presumably erected in happier times.)

The imposing expanse of the South Broad branch of the concourse is a welcome relief. The space is so ample as to allow bicyclists and traveling dance troops to practice their art without fear of jostling the few commuters. All are dwarfed by the massive support beams that liberally stud the cavern.

Turn down the passage toward the 13th Street station, where echoing shouts amplify the bravado of any teenager who wishes to assert herself. Gashes in the ceiling, aged and speckled with rust, present the kind of crevices that viscous liquids very well might ooze from. (Hopefully these will be near the top of SEPTA’s repair list.)

Tired of bleak stretches of untended corridor, we retire through the first relief that presents itself: A revolving door leading to the old Wanamaker building. The stairs lead to a nondescript cafe on the west side of the department store, now a Macy’s. After pausing to enjoy a nondescript iced coffee (this is thirsty work), thread through the imposing boots and glittering jewelry of the women’s section, pausing to pat The Eagle for luck. Then the men’s section, with its neatly ranked four-packs of somber-colored socks. After reaching the main entrance, turn a tight right and return to the concourse.

The final length of dreary corridor, on this side of the Market-Frankford line, leads to an 11th Street exit. Instead turn left through a claustrophobia-inducing passageway and enter the air-conditioned splendors of the Aramark Building and the far western edge of Market East station and The Gallery (a below-ground shopping mall built in the 1970s). Dodge through the shops and food courts filled with teenagers, families and a fair ration of the elderly. The first stretch of stores is fairly mundane, but a claw game filled with Starbucks to-go cups — “Every Cup A Winner!!” — interests us. The task proves insurmountable due to the waxy coat of the containers: “I’ve never seen anyone win,” confides a nearby janitor, who refers us to a claw game where he regularly wins plush toys for his children. (This proves equally insurmountable.)

If we are wise, we avoid the 2 Street Café’s $9 margaritas despite the entreaties of a very kind waitress with fluorescent violet lipstick. The Gallery’s upper stories beckon, but we forge ahead past fish and fruit merchants, booksellers and a variety of vendors selling scented oils. Passing the inevitable Dunkin’ Donuts, we enter Strawbridge and Clothier territory, still marked by a “Seal of Confidence” that no doubt induces different comments today than were initially intended.

Finally, pass through a PATCO station, and enter the Mellon Independence Center at 7th Street. A resplendent fruit and flower stand greets the weary traveler, along with the obligatory Dunkin’ Donuts. Ross Dress for Less inhabits part of the street level and shares the building with the FBI, the DEA, the SEC, Homeland Security and the Philadelphia Parking Authority (or so a security guard informs us as we quixotically attempt to scale the upper stories).

Exhausted we pass by the Bright Side Academy, where swarms of tots keep vigil on our exit. With feet planted firmly on 7th Street’s asphalt, we look south upon its intersection with Market and spy another Dunkin’ Donuts. As below, so above.