Need a quick getaway? May I suggest a stroll over to South Broad Street? Look for the opening in the crape myrtles, follow the juniper-lined path down to the grove, then take a seat in one of the vintage patio chairs, grab a beer, and settle in with a book. You might actually mistake the whoosh of city traffic for the lapping of waves.

It seems only right that an instant vacation should be held in an instant space.

The hideaway in question is the latest addition to Philadelphia's growing collection of pop-up parks, an increasingly popular and low-cost way for cities to carve out green retreats amid the crowded hardscape desert. This one is brought to you by the Pennsylvania Horticultural Society and, to be honest, it's not really hidden. It's right there across from the Kimmel Center, between Spruce and Pine Streets. It just feels as if it were a world away.

You could similarly indulge your escapist fantasies at the Porch, alongside 30th Street Station; at the University City District's new Baltimore Avenue plaza; or at Eakins Oval. As of Thursday, the interior of that glorified traffic circle has been outfitted with Parisian-style cafe tables and christened, "The Oval."

But it is PHS's pop-up that will make you feel you've truly left the pressures of the city behind. That is due partly to the site - a vacant lot cradled between the pocked brick walls of two survivor buildings - partly to good design, partly to beer. OK, beer is a big reason the pop-up is so irresistible.

PHS has assembled pop-up gardens on such vacant lots for the past two summers as a way to take its mission to the streets and put leftovers from its annual flower show to good use. Those installations were artful, but static.

This year, PHS stepped it up by partnering with a restaurant company, Avram Hornik's 4 Corners Management, to offer food and drinks. Hornik, whose many venues include Morgan's Pier on the Delaware River, looked at the site and immediately saw visions of rustic beer gardens.

David Fierabend, of Groundswell Design Group, made it real. His design evokes something between a campground picnic grove, a roadside snack bar, and a lobster shack at the end of a Maine fishing pier. Picnic tables are arrayed under 40-foot-tall Honey locusts trucked in for summer. The lacy Gothic side wall of the Broad Street Ministry, a paint-spattered office building, and ivy-draped rowhouses provide a ready-made backdrop, one that highlights the beauty of Philadelphia's urban ruins.

Food prep (picnic fare comes from the Garces Group) and beer service were set up in discarded shipping containers picked up at the port in Newark, N.J. The pine tables give way to an ingenious amphitheater, carpentered from salvaged shipping pallets and softened by a mismatched riot of outdoor pillows. Thus, the detritus of consumer culture has been repurposed in the interest of civic improvement. At night, strings of sparkling lights make it feel like summer will never end.

The vogue for such temporary spaces began four years ago with the annexing of a couple of lanes on New York's Broadway. The city installed a few lawn chairs and called it a plaza. San Francisco followed with its own version, which involved colonizing parking spaces for tiny "parklets." Both cities have upgraded the spaces into permanent plazas.

Philadelphia built its first parklet in 2011. The University City District now manages two plazas and six parklets. Chinatown and Logan have installed parklets, and recently Collingswood became the first suburb to jump on the bandwagon.

The initial aim was to create amenities in places where such social spaces were lacking. The pop-ups also were meant to help people see forgotten corners of the city in a new way, making them viable neighborhoods again. Because pop-ups are so cheap, cities can easily beta-test the locations. PHS has laid out $20,000 for its Broad Street experiment, which will remain open daily until October.

That block of Broad Street doesn't exactly lack for activity; it sits at the heart of the Avenue of the Arts. Yet, for all the bright lights, the Broad Street cultural district is duller than it ought to be. Despite new venues and private apartments, there has been no investment in public space.

The pop-up, which draws 500 to 1,000 people on an average weeknight, changed the mood. It shows that the ideas advocated during the Avenue of the Art's design competition last fall have legs.

At the same time, you might ask what's the difference between the pop-up and, say, restaurants like Frankford Hall and Fette Sau, the hipster meccas in Fishtown similarly carved out of outdoor recesses in weathered buildings.

For one, you don't have to buy anything to hang out in the pop-up. Even though it borrows its design from German beer gardens, Fierabend wanted to create a place where people didn't feel obliged to drink.

"People spend so much time indoors during working hours," he says. "This is a place to relax, to sit around and talk." He was pleased recently to see two women in their 80s talking, alongside two twentysomethings knitting. Small children clamor to sit on a fragment of an amusement park helicopter ride.

Almost since the pop-up opened in May, PHS president Drew Becher has been asked by visitors to keep the garden open permanently. He responds that it will reopen next year in a new location.

Meanwhile, Carl Dranoff, who underwrote the cost of the Avenue of the Arts design competition, has long had his eye on the lot, owned by the University of the Arts. He would like to combine it with the two buildings on the north side, owned by developer Kenny Gamble, for a residential tower.

Summer doesn't last forever, and neither do pop-ups.