Rosaryville and Seneca Creek State Parks – Rosaryville’s 7.5-mile Perimeter Trail is a twisty, single-track, mountain-biking route around park’s edge. Seneca Creek’s greenway trail winds http://www.dnr.state.md.us/publiclands/senecaguide.html toward Potomac River. Schaeffer Farm Trail Area is popular among off-road bikers, with more than 12 miles of marked routes.
Rosaryville: http://www.dnr.state.md.us/publiclands/rosaryvilleguide.html
Seneca Creek: http://www.dnr.state.md.us/publiclands/senecaguide.html