Subterranea (geography) - Subtopics

Underground lakes Burials Subterranean rivers Subterranean fiction Urban exploration 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 Trenchless technology Semi-subterranean structures Underground construction Air raid shelters