A cave of cat-flap escapes.
A normal passable cave with 2d6 exits. Every escape is a squeeze.
Shoulder-high passage. Push a candle ahead of you. Trail one arm behind have one ahead. Pressed in on every side by rock. No turning around. You kiss the rock. Emerge with bleeding temples and crown from the close touch. Each squeeze is d4 miles long
Building blocks. City blocks. Archeo-city foundation collapse.
Open with the roar of wind, the noise and dust-cloud. An ancient city fell five seconds ago and its foundation stones are in your way. To get through dig the cracks. Whistling wind pipes indicate passage. Claw the stone-soil, Ware the ebon glyphs. Past the 1st dig the endless tilting roof is the flat foundation of cyclopean size, seen from below. (Getting past is easy, worm like a rat below the blocks, getting into the city above is months of work.)
VERTICAL SQUEEZE (PIZZA CHEESE)
Two cave linked only by vertical narrows.
The 1st cave curves like the first letter of your name, the 2nd like the last. They are waist-bend-low. The only place to stand are these irregular holes leaping up (or down) that can barely be navigated. They are drawn out and thin like the cheese linking lifted pizza bits just before the cheese-thread snaps. Some mid-point lateral gaps.
A train sized tube of altered stone.
Starts wide and smooth, the end may spindle out like a tree branch. Rock change tunnel spilling from the blood splatter of a dead gigabeing. The flowing fingers of its alteration intermixing on the walls in madly painted webs. The bloodsplatter sprays every direction. Divine ichor melts the rock, leaves bus-sized blood chunnels in a mighty web*. The god-corpse sinks to slowly orbit the iron heart. Leaves scattered frags of twisting tube. Spooky in there, dreams of a dying pulse.
*If you found them all and mapped them en-mass, accounting for tectonic time, you'd know what kind of weapon killed the god, and solve the crime.
WALK IN THE PARK
There is nothing strange about this cave at all. Do not tell the players this.
MAGNETIC SPRING (CARBONIC ACID)
Violence bleeds the air.
The water crawls up fennite runnels iron rails and spikes. Like a milky fizzy drink. It fucks your compass. when blades come out the water springs alive and dances with the knives. Any miss with a metal weapon catches, beads and pearls of water roll across the blade shining like forgotten mercury. Each clash leaves misty furrows curling in the air. The more you fight, the more you are coated with the pearly viscous acidic slime.
Lung-shaped caves. Full of poison, gales, and fire.
Wind-heart air valve with a rhythmic beat, may be made in ancient times to send gusty flows about the underground. Climb around the jewelled alveoli. Bronchial paths, air loops through. Numerous Oxide helictites with Highly flammable pure O2 wscreaming through the tips. Azathoth pipes. Don't light them or bring flame near. Can become a death-oven very quickly. Other lung can suffocate you, you turn blue inside. They switch. Leap back and forth to survive. May pulsate.
Cave lit by glowing green predatory ceiling grubs
The cave is clear and greenly lit. Wormlight hides the sticky fishing strands. Dex test to move above slow speed. Fat green alien stars winking. Strands will wrap you up. Drift invisibly around you, curl you like stinging fog, slowing you and stuttering your limbs. If caught they hoist you up. Fight and you may pull down a pile of curled-cat sized angry glowing bugs wrapped around like biting fairy lights.
Tunnel through a groaning micro-fault.
One cake-cut of the earth moves counter-wise. Like waves crashing on opposite tracks, converging tsunamis. The entry cave, like dogs jaws fighting, locked together, gripping and growling from the broken stones. Look through the 'teeth' and see a deep abyss. The exit like the toilet roll tube unravelling, pulled from each end, spirals of stone with nothing in-between. The faults may twitch and shatter as you pass.