A hundred feet beneath the desert in New Mexico is a temple built of human bones. For a long time, it could be accessed through a network of caves.

Back in 1975, when I was young and stupid, my cousin Manny and I went down there. The adventure was just too irresistible. We’d heard about it from our own grandfather when he was drunk and raving, going on and on about the days when he was a young stallion.

I’d never seen a thing like it in my life. And I didn’t after. But a dozen of us went down there, and I was the only one who made it. I’ll tell you one thing. You’ll never hear your own heartbeat the same if you make it back.

There was no promise of gold and gems. No Spanish bullion. No stolen riches. Just bones, and a lot of them. For me, 21, never having left the county, much less the state, that was enough.

So we went down there, Manny and I. We’d been caving since our early teens. We knew just enough to get into trouble. We followed the directions through the chambers and connections up top: easy enough if you had instructions. A total fucking maze if you didn’t.

Finally, after an hour crawling through the standard, dank pits, we reached a chamber that smelled like iron. The limestone walls were replaced with something wholly different: bleached white cobblestones, all bound with some kind of ancient concrete.

On closer looks, we realized that the rocks were bones. Toe and foot bones to be more precise. Later, I would learn their names: Calcaneus, Phalanges, Talus, Cuboid.

The chamber itself was about the size of a three-car garage, with five smaller rooms at one side. Manny and I debated the purpose of the place: a temple, maybe, with the smaller rooms serving as confessionals? Or perhaps if had been used for something more mundane, like storage.

As we debated, I became aware for the first time of a thudding sound emanating from deep in the earth far below us.

“Shhh…” I told Manny, and we stopped and listened to the steady beats.

“Sounds just like a heart,” he said after a few minutes. He was kneeling on the floor, running his hands over the tiny, polished bones. “How many people do you think it took to make this place?”

“You mean the builders or the skeletons?” I asked.

“Why assume those two groups are different?” he replied. “Like those workers whose bones are sealed up in the Great Wall. Sometimes, the builders and the materials are the same thing.”

He was silent for a second after that, and the sound of the heartbeat returned. But there was something closer now, a kind of scratching that was much closer. I swung my flashlight beam across the ceiling, but I didn’t see anything but shimmering bones.

“Let’s keep going,” said Manny.

I shook my head. “Maybe this is far enough.”

“I thought you wanted an adventure,” he said. “Now you’re going to pussy out because you found one?”

He started walking away, down toward the end of the room. Reluctantly, I followed.

Connected to the first room was a long shaft, its walls built wholly of interlocked tibias. The bones had been sanded slightly to form clean edges, allowing them to fit together perfectly. A spiral staircase, built of the same bones, ran down the entirety of the shaft, descending deep into the black.

Through the empty air, we could hear the thudding sound stronger now.

Manny led the way as we descended. The bones underfoot were smooth and damp, and we had to walk carefully. The stairs were maybe two feet wide with no rail at all. Once, I almost slipped, but Manny caught my hand, pulling me back to safety. With every step afterward, my heart pounded, matching the thuds filling the air.

“You can feel it, can’t you,” said Manny. “Your heartbeat. It’s matching up with the one surrounding us. We’re a part of this place now, just like these bones.”

He ran his hand lovingly across the wall, and I thought about how many people’s leg bones he had just touched. They had once been living too, just like us. They had eaten and laughed and shit and believed in something. And now they were here, the wall of a room.

About halfway down the shaft, the tibias were replaced with femurs, and the width of the shaft expanded by maybe thirty percent. We still had no idea how long it would take to reach the bottom.

Once or twice, we tried dropping small objects down the shaft, listening to hear if they hit bottom. The first couple of times, it was so far we didn’t hear the plink, but on the third time I dropped a penny and heard it land a few hundred meters down. Fifteen minutes later, we finally reached the bottom.

I wish I had never seen the main chamber. It stretched as long across as a football field, leading to walls of pelvises, all assembled tongue and groove like a horrible puzzle. Unlike the others, this chamber was not empty but held a dozen or more staircases, and ladders too, all leading down to smaller platforms and other stairs. The whole thing looked like some ghoulish Escher painting illuminated by my flashlight beam.

The thudding sound here was almost deafening, so much so that I tore off bits of my tshirt and stuck them in my ears to save my hearing. Manny did no such thing. He seemed to revel in the sound, walking to the rhythm of its beat.

He picked a staircase near the middle, and we walked along a bridge of bones to reach it. The bridge itself connected to a walkway rimming the chamber but I couldn’t see any evidence of additional structural support. Whatever mortar the builders used was all that was holding it up. It felt like we were walking on air.

“I finally get it,” Manny was shouting as we descended past the hundreds of feet of pelvises and the building pieces turned to ribs. With the cloth in my ears and the thudding sound all around us, I could barely hear what he was saying. “We entered a foot… then down the leg… an upside down giant, all built of humanity…”

“You okay man?” I asked, but he didn’t seem to hear. The staircases around us were all converging as we descended.

“An upside down god…” he added, his eyes swimming in the dark. I realized he’d turned his flashlight on sometime ago and was plodding down the steps without even looking at them.

My heart was beating fast now, out of rhythm with the great pounding around us, and I sensed a kind of anger because of that.

Something wanted me to be like it.

I was about to ask Manny how the hell he could even walk without a flashlight when I saw movement out of the corner of my eye. I shone the flashlight beam toward the sound, half of me not wanting to look.

Coming up one of the other spiral staircases was what looked like a tiny creature, no more than a foot tall. It was leaning over the stairs, rubbing at them with its bare hands. Shining the beam around, I saw more of the creatures on other staircases, all polishing the bones.

The thing’s body was covered in gray scale-like skin that glistened in the light. As it moved its palms against the bone, it made a scraping sound, like it was polishing the surface with fine sandpaper.

“Manny,” I yelled. “Are you fucking seeing this?”

“They’re cleaning it up,” he said. “Someone needs to keep it clean.”

“I think you’re kind of missing the point, buddy,” I screamed, trying to get through to him. “What the fuck are they?”

“They’re cleaning it up,” he repeated, not quite there. “Come on, cuz. We’re almost there.”

“I’m going back,” I shouted. “What happens when those little fuckers find us walking on their stairs with muddy shoes? Ten to one says we ended up falling about a mile down this shaft and end up pancaked in the center of the fucking Earth!”

“It’s really not much farther,” he said. “Can’t you tell?”

And it was only then that it dawned on me. He’d been here before.

“Why’d you bring me here?” I shouted. “What are we doing here, Manny?”

He started down the stairs, going faster and faster, no longer worried about slipping. I followed, trying to keep up without plummeting to my death.

Finally, we reached the heart.

There, on the center platform, was a sphere built of what looked like fist-sized stones. It wasn’t until we got closer, that we realized they were calcified human hearts. The sphere contracted and expanded just like a normal heart, revealing some kind of black, rubbery substance beneath.

“It called us and we came,” said Manny. “It doesn’t need much more. Maybe just us. The last few pieces to awaken.”

He took my hand.

“Let’s do it together,” he said.

But I grabbed my hand away.

“We’re leaving,” I screamed, my words drowning in the thudding heartbeats.

“You’ll come back later,” said Manny. “You’ll see. It doesn’t need much more.”

And then he approached the sphere. As he did, an orifice opened on the side, just large enough for him to crawl through. And he did. All I could do was watch, kneeling beside the sphere as I screamed for him to come back.

And then it was Manny screaming. A whirring sound echoed from inside the heart, followed by the sound of liquids squelching. Then the screaming stopped and another whirring started. White dust billowed from the top of the sphere.

Then, after a few seconds, the orifice opened and one of the tiny creatures exited. He was holding a neat stack of bones, all perfectly polished. Without even acknowledging me, the creature met up with several of its friends, passing each of them various bones from the stack. Then they all walked away in different directions, carrying the bones to their appropriate chambers.

I’m not sure how long it took me to escape the chamber. It could have been a few hours or a few days. At some point, I fell asleep and found myself dangling over the ledge of an infinite abyss.

One of the small creatures was there, neatly fitting a femur into the wall. There was one more hole next to it, and the creature looked at me with a small amount of curiosity, as if measuring my length.

I thought for sure that it might take me to the heart. That the thing and a hundred of its friends would process me like I was cattle, draining every fluid and saving only the dry bones for their purposes.

But it didn’t. I realized it was holding a tibia and a few foot bones in its other arm. It took its treasures and ascended past me, ready to complete its work.

It’s been almost fifty years since then, and I still wake nightly to the sound of my own heartbeat. Sometimes, I can hear the other heart beating too, deep underground, waiting for me.

My life has been a lonely one. I suppose I don’t know how to connect. Everyone thinks they want adventure, but they don’t consider the way it changes you. Once you’ve touched the dark, people can see it on you, a black mark they recognize but can’t name.

Everyone hates a man who has seen too many shadows. Think of all the people who’ve come back from war and disappear on the streets. All the addicts slowly decaying under old tarps. I’ve never been on a second date, and all my family and friends are dead. When I walk down the street, people look right through me, like I’m already gone.

And sometimes, sitting alone in my empty apartment, I sip the end of a scotch bottle and think how nice it would be to become a part of something.