One in a Krillion +100DeneholeChalk miners sank a narrow shaft, then hollowed out chambers below.ErdstallA medieval tunnel network with tight squeezes and a still-debated purpose.Deep Cut +85Archive vaultArtificial caveAuxiliary Units operational baseBarabaraBiogas digesterCanal tunnelCatch basinCistColumbariumCryptoporticusCycling tunnelDuct bankEarth lodgeFlood tunnelFogouFreight tunnelGeothermal wellGhost stationGrease trapHiding complexHypocaustHypogeumInfiltration galleryInspection pitLeach fieldMikvehMithraeumNilometerOndolOre passPilesPit latrinePumped storage cavernQargiQarmaqROC postRock-cut churchRock-cut templeRock-cut tombSardabSeismic vaultShaft tombSlurry pitSoakawaySouterrainStepwellStopeStorage cavernStormwater tankSumpSunken courtyard yaodongSunken tandoorTram tunnelUndercroftUnderground aquariumUnderground bathhouseUnderground boiler roomUnderground bus stationUnderground cinemaUnderground damUnderground data centreUnderground factoryUnderground farmUnderground fortressUnderground funicularUnderground gardenUnderground granaryUnderground greenhouseUnderground hangarUnderground hospitalUnderground hotelUnderground libraryUnderground magazineUnderground museumUnderground nightclubUnderground officeUnderground postal railwayUnderground power stationUnderground public toiletUnderground pumping stationUnderground quarryUnderground railway depotUnderground reservoirUnderground restaurantUnderground saunaUnderground schoolUnderground sewage treatment plantUnderground shooting rangeUnderground sports hallUnderground storage tankUnderground streetUnderground submarine baseUnderground substationUnderground telephone exchangeUnderground theatreUnderground warehouseUnderground water tankUnderground water treatment plantUnderground wind tunnelUtility vaultWheelhouseWildlife tunnelWinzeRare +60AqueductBoreholeBurial vaultCave houseCellar dwellingCesspitCisternCrawl spaceCulvertDugoutEarth ovenEarth-sheltered houseElevator shaftEscape tunnelFoundationFoxholeFrench drainIcehouseIn-ground poolKivaManholeMilitary tunnelMine tunnelNuclear waste repositoryOil wellOssuaryParticle acceleratorPedestrian tunnelPipelinePit houseQanatRoad tunnelSecret tunnelYeah, I forget the next couple of lines, but uh, then it goesSeed vaultSeptic tankSmuggling tunnelStorm drainSub-basementTrapping pitTrenchTunnel networkUnderground baseUnderground cityUnderground laboratoryUnderground mallUnderpassUnderwater tunnelUtility tunnelVaultVentilation shaftSchooler +30Bomb shelterCatacombsCellarCryptDungeonFallout shelterMissile siloRailway tunnelRoot cellarStorm cellarSubway stationTombUnderground garageWellWine cellarPlankton +10BasementBunkerMineSewerSubwayTunnel
