You've passed by the northeast corner of 20th and Market Streets so many times, you can't even remember what's there.
For the record: nothing since the Penn Center Inn was demolished in 1990.
But for the next four months or so, the scenery will be dramatically different. This dusty, rocky, weedy, littered and windy lot - three-quarters of an acre overshadowed by Independence Blue Cross and other tall buildings - has been transformed into a huge garden by the Pennsylvania Horticultural Society.
Touted as a "pop-up garden," it's like the short-lived costume shops that set up in empty storefronts before Halloween, then quickly disappear - with a big difference.
PHS envisions this horticultural pop-up as a high-profile, three-season promotion for local food, community gardens, and its many programs, especially City Harvest, which distributes fresh produce to poor Philadelphians through a network of 45 community gardens.
In 2012, PHS plans to "pop up" again - at a different Center City location, according to Drew Becher, society president.
"About 300,000 people come into Center City each day. This can be a billboard of what's going on in community gardens all over the region," Becher said.
Cost of the garden: $80,000, all but $10,000 of it from the William Penn Foundation. Independence Blue Cross and Brandywine Realty Trust, which plan to develop the property jointly, split the difference. Edible and ornamental plants - everything from beets and okra to bee balm and Colorado blue spruce - also were donated.
Monday afternoon, as friends and employees of organizations and corporations that contributed in some way gathered, the new garden made its debut with high praise from Mayor Nutter.
"I have hated this lot for decades because there was nothing going on here," he said. "This shows that agribusiness, and paying attention to land and how we use it, mean so much."
The garden gate opens to the public on Wednesday at noon. From then until at least late October, visitors can stop by on Wednesdays and Thursdays from noon to 2 p.m. for PHS's free tours and half-hour workshops on topics such as rain barrels, organic pest control, flower arranging, container gardening, canning and preserving, and composting.
At other times, there will be scheduled children's programs, group tours and events, even tai chi classes and movies. (For information, go to www.PHSonline.org)
Passersby can see it all through a chain-link fence and large gate left over from Rodin Museum renovations. The gate will be locked when the garden is not in use.
PHS has been taming the site since April, when it was a blur of yellow dandelions. Last week, the pace approached TV-makeover status. That continued through Sunday.
PHS built raised beds, lined them with landscape fabric to squelch weeds, filled them with mushroom compost. Then came planting, watering (with city permission) from a nearby fire hydrant, and sometimes - because of the extreme heat - ripping out and planting again.
"The conditions are challenging, to say the least," said Nancy Q. O'Donnell, a PHS landscape architect.
The garden is literally and figuratively designed around a re-creation of a 2011 Flower Show exhibit by horticulture and landscape architecture students at Temple University Ambler. Called "Écolibrium - French Traditions/Modern Interpretations," it's a greenhouse with colorful glass panes, set on a bed of compacted gravel that serves as foundation and storm water drainage area.
The greenhouse was inspired by the geometric paintings of Dutch artist Piet Mondrian. "We took that design and radiated it out to the whole site," O'Donnell said.
The raised beds are irregular rectangles and oblongs, 10 inches deep, placed inside a perimeter of meadow plantings and filled with herbs, vegetables, trees, and landscape plants; some showcase one or just a few plants, such as corn, sunflowers, zinnias, grains, and tiny Christmas trees.
Six Philadelphia chefs - from R2L, Square 1682, Table 31, Sampan, Barbuzzo and Paradiso - were on hand on Monday with delectable food samples from their restaurants, things like Prosecco with strawberry sorbet and scallops marinated in blueberries. Later in the season, they'll incorporate the garden's produce into their menus, donating the proceeds back to City Harvest.
Similarly, at season's end, the plants and garden artifacts - most made from recycled materials - will be sold or donated to community gardens.
It's all good to Gwen Gittens, who works at Heery International at 18th and Arch and came to investigate the change at 20th and Market. "This was such an ugly lot," she said. "A lot of people walk by here and I guarantee they'll at least wonder what it is."
At that very moment, Joseph Sabatino, a nongardener who works at Verizon, walked by. And he did wonder . . .
"This is better than an open eyesore," he concluded.
When asked if he'd ever venture inside, he paused. "Ah, no," he said.
For a video glimpse of the pop-up garden, go to www.philly.com/popup
Contact staff writer Virginia A. Smith at 215-854-5720 or email@example.com.