GPS: 39°47'N 86°09'W
How many city parks have backcountry? At Eagle Creek Park, the nation's 12th largest urban park at 5,200 acres (2,104 hectares), a reservoir separates the developed east side from the wild west, where no trails penetrate. Make that "official" trails. A spiderweb of unmaintained paths crisscrosses the forested ridges and ravines; it's here that Ed Wright leads a weekly eight-mile (thirteen-kilometer) hike for the Indianapolis Hiking Club.
Vitals: Indianapolis Hiking Club; indyhike.org
Originally published in the April 2008 edition of National Geographic Adventure