subterranea
underground space, natural and man-made underground structures
underground storage
facility where gas is stored underground
rock-cut architecture
creation of structures, buildings, and sculptures by excavating solid rock
Stepney Green cavern
underground junction where Crossrail spits into two branches
subterranean river
river that runs wholly or partly beneath the ground surface
subway
underpass for pedestrians and cycles
wine cave
area for the storage of wine
underground base
base located underground
Cueva de Conan
cave in Spain
missile launch facility
underground structure for the storage and launching of intercontinental ballistic missiles
dugout
shelter for humans or domesticated animals and livestock based on a hole or depression dug into the ground
rock-cut tomb
tomb cut out in rock
Camden Catacombs
system of underground passages in Camden Town, London
lunar lava tube
sub-surface tunnel on the Moon, believed to have formed during basaltic lava flows
Labyrinth of Porsenna
archaeological site
crawl space
enclosed space below a structure that is too short to stand erect in
cave
natural void under the Earth's surface
burial vault
structural underground tomb
underground mine
underground facility for the extraction of minerals
storm cellar
type of shelter
Los Angeles Mall
shopping mall in the Los Angeles Civic Center, USA
dungeon
room or cell in which prisoners are held, usually during the Middle Ages and Renaissance
hypogeum
underground temple or tomb
Primate Wine Cellar
wine cellar in Esztergom, Hungary
deep geological repository
nuclear waste repository excavated deep within a stable geologic environment
volcanic pipe
subterranean geological structure
London deep-level shelters
Air-raid shelters under London Underground stations
lava tube
natural conduits through which lava travels beneath the surface of a lava flow
basement
below-ground floor of a building
cavern
subterranea
cave system
system of interconnecting caverns
casemate
a fortified or armoured gun position - may refer to fortifications on land or to structures on ships or on vehicles
sump
passage in a cave that is submerged under water
underground lake
lake mainly located beneath the Earth's surface
underground city
series of linked subterranean spaces
Kingsway telephone exchange
Cold War-era hardened telephone exchange underneath High Holborn in London
underground structure
man-made underground structure
salt cavern
artificial cavities