Complex sentence: Shirlington lies in the valley of Four Mile Run, a tributary of the Potomac River, and is the site of the trailhead of the Washington & Old Dominion Railroad Trail, a rail trail that travels along the route of a railroad that closed in 1968.
Split into simpler sentences: Shirlington lies in the valley of Four Mile Run, a tributary of the Potomac River. It is the site of the trailhead of the Washington & Old Dominion Railroad Trail, a rail trail that travels along the route of a railroad that closed in 1968.