abandoned
adit
catacomb
cavern
channel
coal
collector
concrete
corridor
dark
deep
derelict
digger
dirt
dirty
drainage
draining
exploration
flood
flow
flowing
industrial
inside
interior
lost
mine
mineral
mining
old mine
ore
passage
pollution
resources
river
rock
sewage
sewer
sewerage
stream
subterranean
toxic
tunnel
underground
underpass
urban
vaulted
waste
wastewater
water