Traversing twisting caverns that never ended and whose beginnings were lost to time, that was Lynne’s passion, her calling. As she stepped down through what seemed to be an arch, crumbled away to simply two pillars of stone, the cavern opened up into a vast expanse. Her torchlight didn’t illuminate much besides the ten feet in front of her, but she had an inkling, a feeling you get after spending so much of your life in caves, that the ceiling had exploded upwards and the space ahead of her would go on for quite some time. She’d been exploring for four hours already, and at this point it would have been best to either set up camp or head back up to the surface. But it called her forwards, that great expanse, and the well-worn path that signalled an old civilisation perhaps once thrived here. It could have been an old Dwarven city, maybe, but she was unsure of any that had existed in this area.
The path winded downwards, spiralling down the side of what felt like a cliff. Torchlight glinted off of nothingness away from its edge, just reflecting off of dust that she had thrown up as rock crumbled underfoot. Back and forth it twisted on itself, and eventually she was almost travelling straight down the cliff face. Carefully placed feet became carefully placed hands as she began clambering down the steps like a ladder, her torch held in her teeth. Her feet came in contact with a flat surface, and with a passing of her torch she seemed to be at the cliff’s base. She shone the torchlight back out ahead of her once more, away from the cliff face, and once again, nothingness, dust.
Smoothed out edges that signalled a continuation of the path from above slithered out towards the centre of the chamber, and she followed them. She had no idea how far the cave extended to her left and right, but at this point the ceiling overhead must have been hundreds of feet away. It was warm here at this depth, almost uncomfortably so. Was she already so close to the upper mantle? She checked her altimeter, one made specially for spelunking. Negative 30,000 metres.
“This must be broken,” she hit the side of the altimeter, hoping the reading would change. The dial swung wildly in either direction before finally settling down once again around negative 30,000. “When did I get so low down?”
Lynne shrugged, she knew the way back up was relatively straight forward from here, with few twists and turns to account for. The entrance was a tiny slit in the ground hidden in an overgrown forest and was about the hardest thing to navigate on the entire journey. It would be easy enough to get back whenever she needed to, she convinced herself.
Continuing to the centre of the chamber, she made sure to place the occasional marker to ensure that she could make it back to the cliff face, and made notes on her map to keep track of her relative location on the surface. About now she would probably be coming under a large river; potentially a number of aquifers fed the chamber in the past, a must for the cave dwellers of old.
One misplaced step was all it took. Her head buried in her surveying kit. She felt her ankle twist below her and the ground swallow her entirely, slipping down a smooth, chamfered edge. She dropped her map, and her torch, watching helplessly as the light tumbled into the unending maw of the abyss. Still falling, albeit rather slowly, she tried to find purchase on the surface she was tumbling down, but it refused her with its smoothness. With a lame ankle and no light, she could do little else but ensure that she was prepared for her landing. It got hotter; warm balmy air being spewed up from the hole, as though this was a portal directly to the planet’s magma table. The lack of red and orange light assuaged some fears that she might fall directly into a river of lava, but it was little comfort. She wrestled her altimeter off of her waistband: negative 35,000 metres and counting. Finally, her torchlight came into view, and she braced herself for impact with the ground. She slid like a curling puck on the now level surface, still smooth as the hole’s edges, and eventually came to a stop as the ground turned to gravel. She clambered to her feet and hobbled over to the torch, shining it around the hole’s base. A cave entrance emerged at the edge of the gravel.
With little else she could do, she located the remnants of her surveying kit, the map still in one piece, as opposed to the shattered remains of her compass. She made an educated guess on the amount of lateral movement she had been subjected to by the hole and made a note on the map of her assumption. The cave’s mouth called to her, and she answered, committed to explore what was most-likely going to be her final resting place. Such was the life of a spelunker.
As she followed the caves smooth edges, she began to see light. But not of magma, or of lava; something altogether unnatural. Out of place. More light, and slowly the cave became bathed in a pale colour, akin to the shining of a full moon.
Her jaw slackened and heart raced as the cave finally opened up. Great towering buildings speckled the horizon; above was a fantastic glass ceiling where the source of the moonlight shone. Some looming artificial light bulb, a manufactured sun for the underground city. Stood dumbfounded looking over the metropolis from above, she noticed its citizens going about their business, manoeuvring throughout the sprawling streets and road system, the sounds of the hustle and bustle of their lives just barely reaching her ears. They looked almost human, but that couldn’t be right. No humanoid could live so deep below the surface. A thriving population that had gone unrecorded, unknown to the world above.
Ignoring the pain of her ankle, she rushed down a set of steps that led out away from her trap hole, towards the city. She eventually reached its outskirts, and there they were. Humans. Odd bluish skin, but humans, nonetheless. They had all the right morphology: no pointed ears like elves; taller than dwarves; no horns; no feathers. By now she was generating stares and glances from the city folk as she began meandering through its streets and alleyways. They spoke a language she couldn’t understand, nothing like she’d ever heard before.
A pull on her arm stopped her in her tracks. One of them had grabbed her, plucked her from the road before a motorised vehicle sped past.
“Thank you,” she replied by instinct.
The cave-human frowned in response, then uttered something in their language before releasing her, and getting on with their own business.
“I’m going to be famous. I’m going to go down in the annals of history! A completely undiscovered, unknown race of humans that live deep underground. This will change the very understanding of our civilisation, of the surface world!” She drew even more stares and odd looks as she ranted to herself in bemusement.
Then, her head was covered in what felt like a sack, her knees were kicked out from under her, and her arms were wrenched behind her back. A rope pushed the sack into her mouth as the first of her screams began to leave her mouth. Handcuffs locked her wrists together and she was stood back up. Through the relatively loose weave of the sack, she could still see the streetlamps and their cool lunar light. She was pushed into the back of a car, and she felt a horrible knot of dread twist itself in the pit of her stomach as the engine roared into action. There may have been a reason why they had never been discovered.
From a prompt on reddit: