Numerous military shelters and underground installations dating from the Second World War, particularly the period of the German occupation, can be found throughout Crete. Some are small and shallow, while others form complex networks of deep tunnels, chambers and passageways excavated into the ground or natural rock.

Many of these installations were constructed by Cretans who were requisitioned or subjected to forced labour by the German occupying forces. Depending on their location and design, they served as air-raid shelters, ammunition and military-supply depots, command posts or protected areas for military personnel. Some tunnels formed part of larger fortified complexes located close to gun emplacements and positions controlling strategic sites.

Their remains survive in towns, near airfields and harbours, on remote capes and at other locations of military importance. Their widespread presence reflects Crete’s strategic significance for the control of the eastern Mediterranean during the war.