abandoned

adit

adventure

bunker

catacomb

cave

caveology

cavern

caving

construction

den

dungeon

elaboration

entrance

excavation

fallout

flows

fortress

gallery

grotto

grunge

grungy

horror

journey

laos

messy

out

passage

paths

pit

potholing

quarry

slabs

speleologists

speleology

spelunking

steps

stones

structure

subway

tonel

travel

tunnel

under

underground

washed

water

worldn