Commanding a vital ford over the River Tweed, Norham was one of the strongest of the border castles, and the most often attacked by the Scots. Besieged at least thirteen times - once for nearly a year by Robert Bruce - it was called 'the most dangerous and adventurous place in the country'. But even its powerful 12th-century keep and massive towered bailey walls could not resist James IV's heavy cannon, and it fell to him in 1513, shortly before his defeat at Flodden. The extensive 16th century rebuilding which followed, adapting the fortress for its own artillery, is still clearly traceable.