Tunnels have been an important part of Dover Castle's defences since Medieval times, although the majority date from the Napoleonic and WW2 eras. There are various separate tunnel systems, including those associated with the Napoleonic outer bastions (East Demi Bastion, Horseshoe Bastion, East Arrow Bastion and Hudson's Bastion) and those at the North-West Spur. The main levels have been given a alphabetical naming convention ('A'-'E'), standing for 'Annex', 'Bastion', 'Casemate', 'Dumpy' and 'Esplanade'. 'Casemate' was built during the Napoleonic era as a barracks; 'Annex' was a WW2 underground hospital facility; 'Bastion' was begun in WW2 as a HQ but was abandoned due to collapse; 'Dumpy' was constructed in WW2 and re-used as an intended Regional Seat of Government in the cold war. Esplanade is located out of the castle grounds at the base of the cliffs and was used during WW2 as civilian shelters. These were Trevannion Caves and Athol Terrace Caves, which were linked by the long Guildford Tunnel. Annex and Casemate Levels are open to the public, as are some of the tunnels at the Spur/Redan and it is possible that further tunnels will be opened in the future.
Dover Castle is owned by English Heritage and is a very popular tourist attraction. The tunnels have been refurbished as of 2011, and house an impressive D-Day exhibition.
One of the Barrack Casemates
Medieval Tunnel leading to Redan
The Redan / Spur Caponnier
Stairs leading between Medieval Tunnels and Spur Tunnels beyond
Guardroom of the Redan
Spiral staircase down to Casemate Level
Passage down to the Casemate Balcony
WW2 Generator room
Upper level of one of the Casemates
Looking out towards the harbour
Passage between the casemates
Entrances to Annex Level (left) and Casemate Level (right)
19th Century tunnel
Lined section in Annex