stone walls, dirt/stone floor, tree roots, dead leaves, twigs, trash, campfire remains, animal scat, fur, old bones, bears, mountain lions, raccoons, bats, rats, spiders, webs, insects, earthworms, stalactites hanging from ceiling, stalagmites protruding from floor, pools of water, underground rivers, bright sunlight at the entrance but diminishing to total darkness deeper into the cave, hieroglyphs/cave paintings, graffiti, water dripping down walls, lichen, moss, crumbling rock, bat guano, animal scat, mushrooms, cracks
wind whistling around stone, muffled sound of wind in trees outside, echoes, shoes shuffling over floor, skitter of animals, insects whirring, bat wings fluttering, water dripping or running, rustle of feet through detritus, crickets chirping, campfire crackling, click of flashlights, voices echoing, loose rock being kicked in the darkness, growls, rumbled breath of a slumbering animal, leaves rustling at the entrance, the squeak and chitter of small animals
Wet or cold stone, animal feces, decaying animals, animal musk, rotting vegetation, stale air, stagnant standing water, briny smell of slimy lichen, woodsmoke/food cooking (if there's a fire going)
Sweat, water, food cooked over a fire (trapped animals, fish, hot dogs--whatever the case) & drinks made or brought (tea, coffee, etc)
Bumpy/knobby/sharp stone, crumbling rock, jamming hands in fissures for handholds, slipping on a patch of wet rock, scraping against the wall, a fist of stone poking you in the back as you lean against a wall, bumping your head on a low ceiling, sweeping aside debris or loose rock, dust on the hands, running a fingertip along a vein of quartz or gemstone (gold, silver, turquoise, etc), walls wet with condensation, walking or swimming through a free standing pool or grotto, the splash of water, water dripping from cracks in the roof, cold wind or snow finding its way into the cave, bones or twigs crunching underfoot, scattering debris with a boot, cold stone floor against cheek during sleep
Helpful hints:--The words you choose can convey atmosphere and mood.
As I opened my mouth to call the all clear, something snapped. I froze, pressing myself against the cold, wet stone, my gaze flicking across the unyielding darkness of the cave. My stomach clenched at the unmistakable scratch of paws passing over debris and a snout snuffling the air, rooting for a foreign scent: me.
Ryma held his torch close to the stone, the orange tongues of fire lapping at drawings set down by his ancestors. Powerful strokes of henna depicted warriors with lynx fur mantles and stone spears, running the Great Hunt for Grandfather Bear. His throat grew thick. His father had stood here--his uncles, his grandfather. Had they looked upon this and reflected on what it was to become a man, to earn the right to a mantle, just as he now did?
--Similes and metaphors create strong imagery when used sparingly.
Example 1: (Simile)
Wind shrieked through the hollows and gaps of the cave like banshees haunting a graveyard.
Example 2: (Metaphor)
This far from the entrance, the darkness was absolute, playing tricks on my sense of time and space. I reached out and placed a hand against the bumpy stone wall, an anchor in this void.