Subterranea (geography)

Petra (; ), originally known to its inhabitants as Raqmu ( or ), is an ancient city and archaeological site in southern Jordan. Famous for its rock-cut architecture and water conduit systems, Petra is also called the "Rose City" because of the colour of the sandstone from which it is carved. The city is one of the New 7 Wonders of the World and a UNESCO World Heritage Site.

right|thumb|upright=1.5|An illustration showing groundwater in aquifers (in blue) (1, 5 and 6) below the [[water table (4), and three different wells (7, 8 and 9) dug to reach it.]]

land warfare involving static fortification of lines

thumb|The Tomb of I'timād-ud-Daulah in [[Agra, India]]

structure which protects against enemy attacks from the air

exploration of usually hidden or abandoned structures

thumb|The entrance of a tomb at the Theban Necropolis—TT 353. The entrance was built by the order of Sen-en-Mut, 97.36m long and 41.93m deep thumb|right|3D 3D scanner|laser scan profile of the [[Hypogeum of the Volumnus family]] thumb|right|Tablinum inside Hypogeum of the Volumni, in the northern end of the crypt thumb|right|3D image of Tablinum inside Hypogeum of the Volumni, cut from a 3D scanner|laser scan thumb|right|Entrance of the Three Brothers' hypogeum in Palmyra, Syria thumb|right|250px|Hypogeum of Yarhai, [[Damascus, Syria]] A hypogeum or hypogaeum ( ; plural hypogea or hypogaea; li

historical concept proposing that the planet Earth is entirely hollow or contains a substantial interior space

rainwater harvesting infrastructure

thumb|Eternal Flame Falls in New York has an eternal flame inside a small grotto behind the falls thumb|Grutas de García in [[Nuevo León, Mexico]]

thumb|Postmaster-General's Department|PMG manholes in a city street, [[Perth, Western Australia]] thumb|Sanitary manhole|Manhole being used to access sewer thumb|Installation of a fiber-optic manhole in Brooklyn, New York thumb|An uncovered manhole in Beirut, Lebanon A manhole (utility hole, maintenance hole, or sewer hole) is an opening to a confined space such as a shaft, utility vault, or large vessel. Manholes, typically protected by a manhole cover, are often used as an access point for an underground public utility, allowing inspection, maintenance, and system upgrades. The majority of u

enclosed space specially designed to protect occupants from radioactive debris or fallout

thumb|The microscopic cave snail Zospeum tholussum|Zospeum tholussum, found at depths of in the Lukina Jama–Trojama cave system of [[Croatia, is completely blind with a translucent shell]] Troglofauna are small cave-dwelling animals that have adapted to their dark surroundings. Troglofauna and stygofauna are the two types of subterranean fauna (based on life-history). Both are associated with subterranean environments – troglofauna are associated with caves and spaces above the water table and stygofauna with water. Troglofaunal species include spiders, insects, myriapods and others. Some

nuclear waste repository excavated deep within a stable geologic environment

urban legend about alligators permanently inhabiting sewers

structural underground tomb

religious community

steerable trenchless method of installing underground pipe, conduit, or cable in a shallow arc along a prescribed bore path by using a surface-launched drilling rig, with minimal impact on the surrounding area

style of house built in a natural or artificial cave

underground structure that disposes of unwanted water, most commonly storm water runoff, by dissipating it into the groundwater

underground space, natural and man-made underground structures

creation of structures, buildings, and sculptures by excavating solid rock

cemetery

waterfall inside cavern

Cataphiles are urban explorers who illegally tour the Mines of Paris, a term popularly used to describe a series of tunnels that were built as a network of stone mines, which are no longer used. The Catacombs of Paris comprise a subset of this network.

monastery

is a passage built underground or above ground to carry utility lines such as electricity, steam, water supply pipes, and sewer pipe

underground museum in Chiaia, Municipality 1 of Naples, Italy

animal species adapted to live in an underground environment

secret subterranean passage used for the smuggling of goods and people

US television program

thumb|Entry to the Ratgöbluckn erdstall at Perg, Austria – its passages are high enough for tourists to access (electric lights since 2002)

low-income migrant workers in China

process of identifying and labeling public utility mains that are underground

Tunnel in Naples, Italy

Wikipedia list page

underground organization

thumb|Souterrain on Canna, Scotland|Canna in the [[Hebrides]] thumb|upright=1.3|Panoramic view of a souterrain contemporary with a ringfort dating to around 700 AD, built within a much earlier barrow cemetery, in County Armagh, Northern Ireland Souterrain (from French ''''), meaning "subterrain", is a name given by archaeologists to a type of underground structure associated mainly with the European Atlantic Iron Age.

type of shelter

WWII bunkers in Valletta, Malta