The Washington & Old Dominion (W&OD) Trail is a paved rail trail that runs through Northern Virginia along a retired rail right of way from Shirlington to Purcellville. A crushed gravel side path runs parallel to the paved route along most of the route west of Arlington County, watch out for equestrians on this side path, especially out in Loudoun County.
Mile markers, benches and water stops make navigating the Washington & Old Dominion a breeze, and interpretive signage and antique railcars trailside treat riders to a local history lesson as they pedal.
Though not a mountain bike trail, it is the backbone of trail connectivity in Northern Virginia. It's used to connect singletrack trails in Arlington and Fairfax counties like the Arlington Singletrack Tour and the Cross County Trail CCT. The stone dust bridle trail on the western portion of the trail makes a great way to get winter miles in when the local singletrack is wet.