A casemate is a large room with a vaulted ceiling in a fortress that was used as storage, accommodation or for artillery that could fire through an opening or embrasure. Since the late 19th century, the term casemate has been used to describe a fortified gun emplacement or armoured structure from which guns are fired, in a fortress, warship or armoured fighting vehicle.
Casemates are not really underground, they are in general built as the lower levels or the basements of a fortress. Nevertheless, casemates are generally considered to be subterranea. We guess it's because most casemates are rather old (several centuries at least) and during the centuries speleothems grew on ceilings and walls from the lime in the cement. Or it's the low temperature and the high humidity which is very similar to a natural cave.
Casemates feature high vaulted chambers, extremely thick walls, often with armoured doors and very often with openings for guns. The actual purpose of these structures remains unclear in most cases. The most obvious assumption is that they are simply structurally useful empty spaces to reduce the amount of stones and gravel and the effort required to transport them during construction. In other words, they were created as structural elements of the building's architecture, and any other use is just an attempt to make them useful because they are already there. And these uses are quite wide-ranging: storage, cellars, armory, connecting corridors and even sleeping quarters for the soldiers.
However, there was a change in fortress construction around the end of the 19th century. In the meantime, artillery had become so good that the inside of a fortress was no longer safe; it was possible to fire ballistically over the walls. So underground structures became increasingly important, they served as bunkers for all the things already mentioned, food and drink, material, weapons and of course the crew. It also became increasingly important to have connecting passages in which troops and material could be moved without being shot at by the enemy. At this time, casemates were built specifically as sleeping quarters without windows, but with air supply, heating and electric light. The same applied to connecting tunnels, which were even equipped with a railway in larger fortresses. The transition is fluid, there is every intermediate form.
In other words, casemates are in some ways the first bunkers. In contrast to the air raid shelters of the First World War, however, they were not intended to protect against attacks by aeroplanes, but against attacks by artillery. The strategy of protecting the rooms with the thickest possible layer of rock or earth remained the same. The necessary infrastructure was also developed here, in the casemates. The main difference is that casemates were only built as part of military facilities. Air raid shelters, on the other hand, were largely intended for the civilian population.
We include on showcaves.com only the most impressive casemates relevant for tourists. This topic would generally require a whole website on its own.