Sure, this is Philadelphia, where naming something for Ben Franklin is about as rare as a chorus of boos when the Mets come to town.

And yes, the practice is even more understandable at the University of Pennsylvania's Morris Arboretum - as homage to the school's founder.

Still, this one's a reach.

"This is the Ben Franklin tree," said Bob Gutowski, arboretum director of public programs, placing his hand on a majestic, 250-year-old chestnut oak. "It had a lot of children; so did he."

Indeed, the name could use some work - Franklin had just three kids, after all. Thankfully, the rest of the 92-acre property in Chestnut Hill doesn't lack for creativity.

Last month, the arboretum unveiled "Out on a Limb," a new exhibit designed to replicate the experience of being in a tree canopy. Beyond housing the branch-clad relic of Franklin's day, the $3 million addition features:

The Bird's Nest, stationed 25 feet in the air and accessible by suspension bridge, is able to fit roughly six people, as well as three hefty replica robin's eggs.

The Squirrel Scramble is two hammock-like nets tucked between two towering trees and hanging roughly 50 feet above the ground.

The Wissahickon Vista allows visitors to take in both the expansive arboretum estate and the nearby Wissahickon Creek from a four-story-high perch.

"The response has been overwhelmingly positive," said arboretum director Paul Meyer. "People are really engaging the exhibitry."

With "Out on a Limb" as the main draw, more than 15,000 people visited the arboretum last month, a 66 percent increase over last summer's July attendance. Nearly 300 new memberships ($55 for an individual, $75 for a family) have been confirmed since the opening. Without a membership, admission is $14 for adults, with discounts for seniors, students, and those who arrive by biking, hiking or riding SEPTA.

The "green" discount is consistent with the arboretum's core mission.

"Everybody loves treehouses," Meyer said. "But the bottom line, as a university institution, we want to teach people about the importance of trees in our community."

To that end, the arboretum offers guided tours of the grounds led by volunteer teachers and scientists, showing off a "stumpery" to illustrate the importance of tree roots, a log cabin to underscore the many uses of trees, and an exhibit called "How Cool Is It?" that gives temperature readings from inside a tree, the ground under the tree, the sunny patch outside the tree's shadow, and the nearby brook.

At each spot, children have the opportunity to stamp a mock passport, signifying their completion of a set of educational tasks.

"People learn best when they're having fun," Meyer said. "The call to action of this exhibit is to plant trees and care for trees. What one thing can you do to offset global warming? Plant a tree."

Of course, human-size bird's nests and vertigo-inducing nets have a way of swiping the spotlight. And that's just fine with arboretum officials. As the famous saying goes, they'll come for the giant blue eggs, they'll stay for the conservationism.

"Stuff like this can get really boring for teenagers, but this is pretty cool," said Issie Ivins, 13, from Mount Airy. "You feel like you're a bird.. . . You can see how small their house is."

Issie's brother, 10-year-old Gabriel, prefers the perceived danger of the Squirrel Scramble. He had seen something like it before, he said, when the family lived in London. But scurrying along this tightly knotted nylon injects some added adrenaline.

"I like that you're up so high, and you're not on a little walkway; you're just on a net," Gabriel said. "It's really fun."

The elevated platform of "Out on a Limb," which is entirely accessible to those with disabilities, also has served recently as a yoga classroom. For $25 ($20 for members) on a given Sunday morning, visitors can contort themselves into Downward-Facing Dog, staring at 50 feet of free-fall.

The arboretum hosts a weekly Thursday night concert series as well. Held in the Azalea Meadow, the event features tunes ranging from smooth jazz to kid-ready sing-alongs. Meyer says the staff even has booked wine tastings at "Out on a Limb."

And for those who don't find saxophones at sunset or merlot by moonlight quite romantic enough, the soothing sway of the Squirrel Scramble might prove a haven.

"This is the Dating Scramble," Gutowski said, reclining with his back on the netting. "You always see couples out here on the weekends."

Even Meyer has indulged.

"I have been out here after hours," he said, "with a couple friends and a bottle of wine."

Now that sounds more like Franklin.

If You Go

Morris Arboretum, 100 E. Northwestern Ave., Philadelphia.

Hours: 10 a.m. to 4 p.m. weekdays, 10 a.m. to 5 p.m. weekends, 10 a.m. to 8:30 p.m. Thursdays in August.

Admission: $14 adults, $12 ages 65 and older; $7 children ages 3-17, students, and those who arrive by biking, hiking or riding SEPTA.

Information: 215-247-5777, www.morrisarboretum.org.

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Contact Matt Flegenheimer at mfleg@sas.upenn.edu.