The Four Mile Run Trail is a 7-mile long, paved shared use path in Arlington County and Falls Church. It runs along Four Mile Run from Benjamin Banneker Park in Falls Church[1][2] to the Mount Vernon Trail near Ronald Reagan Washington National Airport, where Four Mile Run empties into the Potomac River. The trail runs roughly parallel to parts of the Washington & Old Dominion Railroad Trail as it follows Four Mile Run, sometimes on the other side of the stream.[3]