The Knobley Tunnel Trail, also known as the Carpendale Trail, is a short but scenic rail-trail spanning only 0.8 miles. Bikers can check out the 1,500-foot tunnel through Knobley Mountain and a 386-foot wooden bridge over the North Branch of the Potomac River. The Knobley Tunnel Trail connects directly to the C&O Canal Towpath near mile marker 183, and is not always open, so check for posted signage.