Dover Castle

The Constable's Gate at Dover Castle, which has been the castle's main entrance since it was built in 1217–21. Commanding the shortest sea crossing between England and the continent, Dover Castle has a long and immensely eventful history. Known as the ‘key to England’, this great fortress has played a crucial role in the defence of the realm for over nine centuries, a span equalled only by the Tower of London and Windsor Castle.