Penn bought the 14-acre lot in 2007 and combined it with existing land to create the 24-acre Penn Park. It features two athletic fields, a multipurpose stadium with 470 seats, a tennis center, and parking for 210 cars. In addition, there are two acres of open space and a picnic grove.
The park, which has 530 newly planted native trees, gives the urban campus breathing room and offers everyone a new vantage point for viewing Center City.
When the site was a parking lot, only the postal drivers who used it could appreciate the expansive sweep of skyline from the west bank of the Schuylkill.
Now that the area is accessible to all, it gives visitors a "big sky" view of the city, said David Hollenberg, an architect for Penn. "It's Philadelphia's Montana."
Penn Park is bordered by Walnut Street to the north, Amtrak rails to the east, SEPTA tracks to the west, and South Street to the south. It's accessible via three walkways, from Walnut, South Street, and Franklin Field.
Built with donations and university funds - no public money - the park was difficult to redevelop, said Anne Papageorge, vice president of facilities and real estate services at Penn.
The park sits in a bowl and is crossed by three rail lines: Amtrak, CSX, and SEPTA. Under the asphalt of the former parking lot were unstable layers of rubble, cobblestones, and dredged silt. When construction began two years ago, workers spent the first couple of months driving 2,200 pilings from 20 to 55 feet long into the ground to support fields and berms.
"There's a lot of work below ground that no one sees," Papageorge said.
The soil also was too poor for planting trees or grass. "Not even a teaspoon that we could use," said Laura Solano, a landscape architect for Michael Van Valkenburgh Associates, which designed the park.
Caravans of trucks dumped 45,000 cubic yards of planting soil to create berms and swaths of open space. Architects created a varied landscape around the two regulation-size athletic fields. Under the CSX trestle that cuts through the length of the park are small hills covered with grass as thick as shag carpet.
"It's a wonderfully textured park and not just all flat," Gutmann said.
The playing fields are covered with synthetic turf made from recycled products. Underneath them is a 300,000-gallon holding tank for storm water, which can be recycled for irrigating the park.
Penn used to be criticized for being too much of a fortress with its back to the city. Judith Rodin, Gutmann's predecessor from 1994 to 2004, began opening up the campus and investing in the surrounding community.
Gutmann took it one step further and announced in 2006 a vision for growing the university eastward along Walnut over the next 30 years. Another keystone project is the $80 million Krishna P. Singh Center for Nanotechnology, across from Penn Park.
When Penn Park was in the design stage, Gutmann insisted on having a walkway to draw people down from Walnut in addition to steering them from campus via the existing Paley Bridge.
"A year from now, people will not be able to believe how we did without it," Gutmann said. "It will be such an essential part of welcoming people not affiliated with the university into West Philadelphia."
The park, which will be patrolled by Penn security, is open to the public from 6 a.m. to midnight. Athletic facilities are primarily for the Penn community, but can be made available to accommodate special events.
In winter, a seasonal inflated structure will be erected over one of the sports fields - Dunning-Cohen Champions Field - for year-round activity.
For more information about the park and guidelines on how to reserve fields, visit pennpark.upenn.edu and click on the "Penn Park" link.
Contact staff writer Jennifer Lin at 215-854-5659, email@example.com, or @j_linq on Twitter.