C&O landmark tunnel built in 1850, cut through 3,118 ft. of rock; a major engineering feat. Towpath, park, picnic facilities. More on Search.visitmaryland.org
Paw Paw Tunnel, part of the C&O Canal National Historical Park, started in 1836 when engineers decided to build the C&O Canal right through, rather than around, an intervening mountain. Th... More on Frommers

