Subterranea (geography) - Subtopics

Underground lakes Burials Subterranean rivers Urban exploration Subterranean fiction Sinking rivers Ancient Roman tombs and cemeteries in Rome Chthonic beings Petra Subterranea of the United Kingdom Mines Subterranean buildings and structures Rock-cut architecture Caves Subterranea of the United States Manholes Semi-subterranean structures Trenchless technology Underground construction Air raid shelters