Berwick's superb walls were begun in 1558 to reinforce an earlier set built during the reign of Edward II. They represented state-of-the-art military technology of the day and were designed both to house artillery (in arrowhead-shaped bastions) and to withstand it (the walls are low and massively thick, but it's still a long way to fall).

You can walk almost the entire length of the walls, a circuit of about a mile. It's a must, with wonderful, wide-open views. Only a small fragment remains of the once mighty border castle, by the train station. The tourist office has a brochure describing the main sights.