The North East Coast was vulnerable during two World Wars. As a result many defensive structures remain. In addition to pillboxes and tank traps, defensive trench systems survive at Crimdon Dene, Blackhall Rocks and Castle Eden Dene. There are impressive trenches at Hawthorn Hive Point. In addition twelve surviving pillboxes have been identified overlooking access points such as the mouth of the denes. Tank traps also survive across three of the denes.