Philadelphia: Blue Mountain
Credit: Songquan Deng / Alamy

Just outside the "City of Brotherly Love," Blue Mountain's Pinnacle, a rocky promontory, affords stunning views of Berks and Lehigh counties. If you follow the 9-mile loop past Pulpit Rock before arriving at the summit, you'll be hiking part of the Appalachian Trail. Just be prepared to scramble – the trail is rocky.