Dover: Castle - Secret War Tunnels 
Description
Originally built at the time of the Napoleonic wars the tunnels were subsequently used as a nerve centre during WWII. The tunnel leading down from Canon Gate takes you to a small museum, café and toilets. To see inside the tunnels you need to take the Operation Dynamo tour
Charge
Included in Castle Entrance fee
Getting There
Latitude: 51.126405; Longitude: 1.323326
What3Words: commented.penny.pets
