Dover Castle is better known as the "Key to England". It was a bastion agains invasion from Europe.
You can see it from miles around. On a clear day, you can even see France from it. William The Conqueror started to built rudimentary defences, and then the castle was improved over the Centuries.
During WW2, the castle and its tunnels played a major role during "Operation Dynamo", where it was the command centre to evacuate the troops from Dunkirk.
The White Cliffs, made of chalk are also a symbol of Dover. It is very popular to walk on it.
