Dover Castle has been called the 'key to England', which is no surprise given its position as the nation's front door. Crack the lock here and you're in - something no hostile power has ever managed, thank goodness. Standing imperiously on top of the famous white cliffs, Dover Castle has been occupied since at least Roman times and is the undisputed master of reinvention.
Peverell's Tower was added by Henry III in the 13th century as an extra buttress of defence. At one time a prison, today it sleeps two in liberating comfort. It has spectacular views - you can see France on a clear day. Wander around the vast site at your leisure and be the first in the queue to tour the re-presented Great Tower, where Henry II held court in sumptuous style.
The new 'Operation Dynamo: Rescue from Dunkirk' exhibition tells the story of Britain's Finest Hour. Churchill called it a miracle and nowhere do his words resonate more than here in these cramped secret tunnels.