All journeys end at the beginning.

So it was that four Philadelphia artists gathered to launch an epic trek - epic thanks to its arduous length, difficult terrain, and mystical purpose - at 61st Street and Baltimore Avenue.

Undertaken at the end of winter, this quest, like most others, became a study of itself and of the travelers themselves. And when the travelers arrived back where they started, they knew the place for the first time.

"I feel like I've been shaken up in this interesting way," writer Ann de Forest said when the trek was over and she was standing in front of Caribbean Cuisine, about to hop on the 34 trolley.

"I feel like I've gotten to know the city," de Forest said. "I've lived here for more than 30 years, but I feel I've experienced Philadelphia in a much deeper way than I ever have before."

What had de Forest and her three companions done?

You can find out firsthand from 6 to 8 p.m. April 27 at the Philadelphia History Museum on South Seventh Street, when the group will share their "findings" in public. You can RSVP here. And they'll do it again at the museum on May 6. RSVP here.

Over five days, they walked the borderland of Philadelphia, sticking as closely as possible to the city line. A link to the interactive map of the route is here.

For 103 miles (65 miles or so as the crow flies), they ventured through dark and littered woodlands, forded roiling streams, dodged cacophonous, puddle-splattering traffic, clambered up and down steep gullies, ventured past firing ranges with a tattoo of gunshots splintering the air, ambled through airport wastes, and listened to the utter stillness of wetlands at dawn as grasses swayed and herons poised to strike.

The journey grew out of a 2013 Knight Arts Challenge grant. Adrienne Mackey, 34, founder and creative force behind Swim Pony Performing Arts, an almost indefinable Philadelphia performance group, cooked up the idea.

Mackey wanted to bring artists from different disciplines together for weeklong residencies. They would all talk, feel one another out, and come up with a project. They would, as it were, engage in creative "cross-pollination," as Mackey calls it.

There would be no preconceptions, no pressure to create finished pieces, no goal but to open up the artistic process in unpredictable ways. At the end of the residency, some kind of public presentation would be held.

There have been several residencies already. This particular one involved de Forest, an author and design and architecture writer; photographer Jacques-Jean Tiziou; Mackey; and Sam Wend, Swim Pony artistic associate.

Mackey brought de Forest and Tiziou together in fall 2015 to see whether they could all work together and to figure out what the work would involve.

"From the beginning, there was always this idea of walking," said de Forest, 60, traipsing north on Cobbs Creek Parkway toward Mount Moriah Cemetery. "J.J. and I talked about doing processionals and something that was ritualistic and formal. And then we talked about themes, and we kept coming back to this idea of edges, margins, and, all of a sudden, as these things do, I think J.J. said, 'Why don't we walk around the city?' And we all said, 'Yes!' "

Tiziou, listening to the conversation, nodded.

"Oh, yeah," Tiziou, 37, continued. "We can do that in four days. It got to be a little more of an adventure than we anticipated."

For one thing, they discovered, the border of the city is not always very accessible. It isn't always possible to follow Poquessing Creek in the Northeast, or even the Delaware River. But they tried to hew as close to the line as possible.

Intriguing landscapes and inclement weather led to nonboundary adventures, of course.

On the first day, for instance, headed north, they stumbled on a rusted-out car hulk mysteriously sunk into the mud in the middle of Cobbs Creek Park. Heading out of the woods, they came upon the Cobbs Creek Golf Course and an isolated field studded with yellow and white golf balls.

Rain was hammering down. They sought shelter in the golf course clubhouse and were welcomed in by surprised duffers-in-waiting.

The duffers warned them about walking alone through North Philadelphia. Their warning turned the trekkers' thoughts toward a reflection on race and privilege.

"There's this weird dynamic of doing this simple human thing, like walking in public space," said Tiziou, nearing Mount Moriah. "But having been welcomed in questionable territories and invited to use bathrooms, you also realize that other people might not have the same experience."

"Yes," said de Forest.

And the opposite is also true. Some places were a little unwelcoming. Parts of the airport were verboten, and some residential areas were not entirely hospitable.

"There was a moment in Bridesburg where a group of young kids on bikes were aggressively angry with us for walking through their neighborhood and taking pictures of things," said Tiziou.

But such moments were rare.

Many people wanted to share their own experience of their spaces: The guys in the Northeast who sat in a car to smoke cigars because they weren't allowed to do so in the house; they knew everything about the neighborhood.

Then there were the guys by the Delaware River who wanted to drive the trekkers to see eagles near Tacony Creek.

And for every moment of blaring horns and embankments covered with debris - hundreds of shopping carts behind Franklin Mills Mall, a field marked by mounds of illegally dumped construction material near the airport - there were sublime moments of peace and great beauty. Pleasant Hill, near Glen Foerd by the Delaware, seems a still, soft, other world; Heinz Wildlife Refuge, near the airport, muffles all things industrial nearby.

And woods.

"We definitely realized how huge Fairmount Park is walking around the edge," said Mackey. "It's just unbelievably vast. If I had to take away one thing that surprised me the most, it would be how much wooded area there is - I'm sure throughout the city, but in particular on the edges. I know it's an urban environment, but it feels in a funny way connected to nature on the edges of the city."

"Sometimes," said de Forest, "we walk where people walk and sometimes we walk where it's not common. That gives you a very different perspective on things - to be a pedestrian in places where pedestrians don't usually go. Like seeing the underside of the Schuylkill [Expressway]."

She continued: "There's something about walking the city and claiming it - this, too, is Philadelphia! - that expands your sense of belonging and community, which is that wonderful thing about living in a city."