GPS: 40°00'N 75°58'W
Wissahickon Valley was once counted among the nation's industrial centers‚ but that was 250 years ago. Today nature has reclaimed this steep gorge in Philly's northwest quadrant. Set out on a seven-mile (eleven-kilometer) loop from Valley Green, heading to Bell's Mill Road on the Yellow Trail. Return on the Orange, Lavender, and White Trails on the other side of Wissahickon Creek. Expect small waterfalls, hemlock pockets, and quad-killing ascents.
Vitals: For maps, visit www.fow.org.
Originally published in the April 2008 edition of National Geographic Adventure