Parkour Enthusiasts Rediscover The American City

"Gabe Streisfeld, 18, grabs a metal pole on a loading-dock ramp in an alley next to the Comcast Center. It feels sturdy, anchored in a cement ledge, so the Penn Valley native takes a few running steps, leaps up about five feet, and swings his whole body around.

His longtime friend Ty Soehngen, 18, of Narberth, suggests they swing halfway around and jump onto a ramp a foot higher. He flies off the pole and grabs a rail above the ramp to hoist himself over.

For Streisfeld and Soehngen, Center City is a grown-up's playground. Both are devotees of parkour, an extreme sport created in France almost 20 years ago that migrated to the United States about six years ago, and more recently to the Philadelphia area."