Photo © Mike Quinn

Harrow's Scar Milecastle can be found just to the east of Birdoswald Roman Fort where the wall would have crossed the River Irthing. Also known locally as Willowford Bridge, the east abutment has survived, although because of the westward movement of the river it is now some distance from the river. The west abutment has been entirely eroded away by the river, leaving only the remains of the small fort.