The 1,800 acres of Wissahickon Valley Park are part of Philadelphia’s 9,200-acre Fairmount Park, one of the largest city parks in the world. A lovely, wooded valley with Wissahickon Creek running through its entire seven-mile length, the Park extends from Chestnut Hill in the north to Manayunk in the southwest. Forbidden Drive, a wide gravel road closed to automobile traffic, parallels the Creek and the Park is criss-crossed by more than 50 miles of often-rugged trails.