Underground (geography)
In geography, underground or subsurface referred to an area below the surface of a planet. Underground structures could be man-made or naturally forming geographical features. A subsurface chart or subsurface scan could detail these areas.

In 2365, on the planet Iconia, Lieutenant Commander Data detected a vast underground power source which was controlled by a console. ()

See also
 Basement
 Bunker
 Catacombs
 Cave
 Cellar
 Dungeon
 Ground water
 Lava tube
 Master subsurface pump
 Mining
 Tunnel

External link
 
Landforms