Not far from Xunantunich there is a cave of natural wonders and human horrors- Actun Tunichil Muchnal. The Mayans believed these caves to be the underworld, Xibalba (literally, “a place of fear”) and visited them to commune with the death-gods within. These caves hold clues to the nature of the sudden collapse of Classic Mayan civilization and its desperate attempts to save itself.

After hiking for a few miles and fording three rivers, my party reached the cave entrance and found archaeologists and photographers at work studying the site.((Unfortunately, camera’s weren’t allowed inside due to prior tourists clumsily crushing ancient artifacts with dropped cameras, so the photos in this post come from official sources.)) I turned on my headlamp and dove into the cave-chilled water. Our guide, Hugh, led us as we swam through the entrance and into the darkness beyond.

The caves themselves are a marvel- I now understand Gimli’s cave fetish. stalactites the size of telephone poles glitter with crystallized calcium. Vaulting ceilings stretch 40ft high. The caves open into an enormous cavern dubbed the “Cathedral” that’s so large my headlamp scarcely illuminates the far wall. With our powerful LED lamps we can appreciate the full scale and beauty of the chamber, but the Mayans’ torches would’ve scarcely penetrated the dark, leaving them surrounded by unnatural shadows reaching out from the echoing void. My mind continuously returned to contingencies for if our lights failed. Could I find the way back? I could follow the river’s current, but there are places where we had to boulder up and down twenty feet of wet, sharp rocks. I regret proudly deciding not to overpack a waterproof flashlight. I stick close to Hugh for his deep knowledge of Mayan history and culture, but also because he has the strongest light.

We emerged from the subterranean river to the dry upper chambers about 3km into the cave complex. We squeezed through a narrow gap in the rocks that opened into a cavern hundreds of feet long filled with shattered pottery, smoke marks, and bones. A lot of bones. Hugh began to tell us of the fall of the pre-classical Mayan cities and the rituals that were performed here.

The Mayans constructed pyramids in sets of three such that the outer two aligned with the solstice sun. Mayan kings would address their people on these days to announce the coming rains. Royalty didn’t claim to control the rains, but declaring when they would come gave them legitimacy in a sort of Mandate of Heaven way. The Mayans’ mastery of calendars, artificial reservoirs, and use of burning wood and limestone to create cement allowed them to build monumental cities and grow to 2 million in population. But one year the rains didn’t come.

The priests made sacrifices of corn near the dim light of the cave entrance. But the rains did not come.((Actually, the probably did come, but the latest research posits that even a 15% reduction in annual rainfall would’ve had severe agricultural consequences for the Mayans.))

The population began to doubt the authority of royalty, and unrest ensued. In order to restore the rains, the priests ventured deeper into the cave and practiced bloodletting by torchlight, even cutting off their fingers as sacrifice to Chaac, the rain god. The shamans believed that by braving the darkness to enter the domain of their gods, their sacrifices might be better received (which seems logical enough). But the rains did not come.

The Mayans believed that the gods had made humans from corn, and when still the rains did not come, the shamans were driven by desperation to offer the ultimate sacrifice of corn- human lives. Those chosen were not virgin women or conquered slaves, but men of high birth and status. It is human nature to believe the world works by causality and reciprocity– no pain no gain– so the Mayans held nothing back in sacrificing the best among themselves. As famine and rebellion spread, even children and infants *selected for their purity) were tortured and slaughtered as offerings to Chaac.

But there’s no rule that pain must bring gain. It’s ingrained in human nature to believe that paying a steep price will earn a commensurate benefit- nearly every pre-modern religion involves ritual sacrifices. But sometimes our sacrifices are just wishful action.

There’s evidence that the Classic Maya had weathered droughts before, but the conditions around 800AD were exacerbated by an energy crisis. The Mayans relied on the jungle’s wood for fuel, and extensive deforestation is theorized to have made the Yucatan lowland climate more arid. The skills and traditions that had let the Mayans flourish for a thousand years were suddenly mismatched to their new environment.

One of the final skeletons in the cave is the “Crystal Maiden”((new analysis shows this is actually a Crystal Dude, but the original name is catchier. I’d have gone with an alliterative neuter, “the Krystal Kid.”)), whose bones and skull are covered in crystals from rising and falling water over the centuries. The child had been bound, tortured, clubbed, and left to rot where he fell. After 900AD the sacrifices stopped and the cave was abandoned. The Mayan survivors fled to the still arable highlands, and cities that had stood for a thousand years were swallowed by the jungle.