abandoned
background
catacomb
cave
cavern
cellar
coal
construction
copper
corridor
dark
deep
dig
dirt
dirty
dungeon
dust
entrance
excavate
facility
geology
hole
industrial
industry
inside
interior
iron
light
long
material
mine
mineral
mining
narrow
old
passage
primary
rail
railroad
railway
resource
rock
secret
shaft
spooky
structure
tunnel
underground
work