32. Prince William Forest National Park

With 37 miles of hiking trails meandering through the 15,000 acre, Prince William Forest Park has the most extensive hiking trail network in Northern Virginia. It is the largest greenspace in the Washington, DC metropolitan region. Where else can you hike an 18 mile loop and get back to Washington, DC for dinner? 

Trail guide. Park map.

Directions: Take I-95 south to exit 150-B to Joplin Road (Va. 619 west). The park entrance is the second right.