NY 659-662 Northumberland England
Thirlwall Castle is an early 14th century stone fortified L-plan hall-house, founded by John Thirlwall. Standing to roof height, the large rectangular block is of four storey, with turrets and a five storey tower projecting from the angles. Supported on a man-made platform and built entirely of Roman masonry from Hadrian's Wall, there are the remains of a walled barmkin, to the south-west. A mile south is Blenkinsopp Castle and 3 miles west is Birdoswald Bastle.
Thirlwall Castle is located north of Greenhead, off the B6318. 4 miles north-west of Haltwhistle, on the A69-B6318.
The site is managed by the Northumberland National Park Authority and is freely accessible in daylight hours.
There is a car park on the B6318.