The World’s Largest Cave Shaft

February 2019: Over a decade and a half ago, I watched the nature series Planet Earth on Discovery Channel.  The episode on the worlds greatest caves opened with the narrator, famed English naturalist David Attenborough, saying “This is the planets final frontier in a world where only the most adventurous dare to go”. Next a man base jumped into the enormous opening of the cave and disappeared into its black depths. The cave was so deep according to Attenborough that the base jumper could free fall from the top for 10 seconds before needing to deploy a parachute. This was the moment I knew that some day I would need to explore this cave. 

The cave located near San Luis Potosi, Mexico on Haustic indigenous tribal land  is known in Spanish as Sotano del las Golondrinas or the Cave of the Swallows. The cave is named after the millions of little birds-cave swiftlets that call it home. It is the largest known cave shaft in the world and to reach the bottom a descent by rope of over 1,400 feet is required.

 In February, 2019 my dream of descending into the Cave of Swallows was realized and I organized a weekend trip with four good friends into the cave. Our plan was to rappel into the Cave of the Swallows, and a second cave in the area, Sotano Del Cepillo. Then time permitting raft down the turquoise green Tampaon River.

How to Get to the Cave of Swallows
Mountains near Aquismon

Via an afternoon direct flight, we flew from Tijuana to San Luis Petosi. Then a driver I pre-arranged picked us up at the airport and drove us  5-6 hours to the small town of Xilitla, where we arrived late in the evening, met our cave guide, discussed a tentative plan for the weekend and spent what was left of the night sleeping in our budget hotel. Early the next morning at 5am we departed for the cave of the Swallows near the Huasteca indigenous village of Aquismon.  From Aquismon, there is a narrow road that was recently paved as a gift to the local people by a previous Mexican President who rappelled into the cave. The narrow road winds and bends as it ascends through rainforest for about 30 minutes until it arrives at a small village where you turn off onto a gravel parking lot. From there, a steep walking trail maybe a mile long, leads down to a viewing platform that overlooks the opening of the cave. 

Huastec Indian Woman
Rappelling 1400′ Into the Cave
At the trailhead  our guides arranged our permits. Then a team of local Indians from the village was selected to carry our rope and climbing gear down the long foot path to the cave’s entrance. This same team of Indians would lower us 1,400 feet into the cave and then lift us 1,400′ back out again. This would all be done by hand and without any mechanical assistance to minimize any disturbance to the cave swiftlets. The cave swiftlets, which the cave is name after, depart the cave via a huge dark swirling exodus every morning.  By the millions. they fly hundreds of miles to the ocean to gorge on small fish and then return to the cave before sunset to sleep, only to repeat this routine the following day. The birds typically leave at sunrise and return by sunset. 


In order to protect the cave swiftlets, the local village only allows cavers to enter and depart the cave when the birds are absent. A bird spotter will give the green light to the lead cave guide when most of the birds are gone and it is allowed to enter the cave. If the weather is rainy or cloudy, the birds may not leave the cave. In this case no one is allowed to descend into the cave and during certain periods of the year when weather is typically bad no one may be able to enter the cave for days or weeks. Even if you could enter the cave when the birds are present, this would be ill-advised since the birds are fiercely territorial and have a tendency to harass climbers. In my opinion climbers have enough to worry about without vicious marauding birds.


Select video above to watch the daily swiftlet exodus

Our climbing rope, all 1,500′ of it, was rolled into a large wooden spool. It was anchored to two different locations. The first anchor was a large boulder and the second a tree that hung over the precipice of the cave. The rope we were told was top of the line climbing rope and replaced every 6 months to ensure that the rope doesn’t deteriorate to an unsafe condition. About 10 or Indian men and boys from the local village prepared the rope to lower us into the cave. Our caving guides began to prepare us. The descent if everything goes as planned is meant to take 30 minutes.  I volunteered to go first, mainly because I just wanted to get it over with. I put on a climbing harness and awaited further instructions. The climbing guide was the first to tie into the rope and he was lowered over the edge of the cave. Then on the rope about 5′  above him I was attached. Another climbing guide that was to stay on top and coordinate the rope handling operation tested all of my connections one last time and then asked me to lean backwards over the edge. I leaned back and let the rope support the full weight of my body. Then I was lowered 5′ over the edge. My feet dangled over the black abyss below me. I looked down but could not see the bottom. Then above me two other Mexican guys were attached. We were all attached to the same rope and we were about to be lowered at the same time. 


Frank tied into the rope hanging over the edge of the cave

The Cave of the Swallows is a pit cave or a vertical shaft. It is shaped like a bottle (see diagram to the right) and the entrance at the top is 200′ wide but shortly below this the ceiling widens to well over a 1000′ across. As I found out as I was lowered another 5′ the wall of the cave quickly gave way and now I was freely dangling in open space.  I felt the rope jerk and twist as we continued to be lowered. We were lowered for 5-10 second intervals to keep the friction from becoming too great on the rope. On the top the men would lower our rope by hand through a small metal bracket to keep it from slipping or getting stuck. 

Because the height of the cave is so great, there is a lot of friction on the rope, and to lessen the friction one man will continuously spray water on the rope from a spray bottle.    

Local men and boys lowering us into the cave
My Friends Descending into the cave
As we descended more, the pressure of the rope pushing against my groin was painful but as I looked out around me into the vast emptiness that surrounded me I realized that any snafus with the rope or our climbing equipment would lead to a quick and guaranteed death. The discomfort of the rope couldn’t have been further from my mind.  After 5 or so minutes of descending the bottom of the cave carpeted in lichens and boulders became more apparent.
Probably when we were 500′ from the top, I felt a jerking sensation on the rope and metallic clicking sounds that I didn’t notice before. I didn’t think too much of it until I heard my guide below me speak to the two guys above me in Spanish,  What was that noise.” They responded, “We aren’t sure.” Then the guide with his walkie talkie directed the guys on top to lower us faster. Their response was we cannot the rope is smoking too much. When I heard this, I couldn’t help but to feel a slight sense of terror due to how helpless I currently was and even though I knew that there was no point in asking the guide if everything was ok since I knew he would only tell me what I wanted to hear, I asked him anyways. His response was as expected, “yes all ok.”
The small dot in the sunlight is my friends descending

Click the Video above of the Ascent/View from the Rope hamging a Thousand Feet in the Air

After what felt like an eternity, we finally reached the bottom and the guide disconnected my carabineers. I looked up to see how far I came. The reality of how high my rope stretched above just couldn’t register in my mind. 

Me Looking Up to the Entrance of the Cave and Rope I Just Descended On

The Bottom of the Cave
Now our entire group safely reached the bottom of the cave and our guide informed he would lead us around the cave. He very sternly directed us to never remove our helmets. He said that even a rock the size of a quarter falling from the ceiling of the cave could generate enough velocity to kill a person. 

See video above of inside of cave

There aren’t really any beautiful cave formations at the bottom of the cave. The main attraction is the magnitude of the chamber you are standing in and knowing that few people in the world have been here. 

Probably the last thing that I needed was to be reminded of someone that previously died in the cave. Our guide showed us a memorial to a man that perished in the cave when his parachute failed to open properly when base jumping. The cave was once popular among extreme base jumpers but it has since been banned by the Huasteca people because it disturbs the birds.  The Huasteca people have a strong bond with nature and even though they seek to monetize the cave, they have done a great job of protecting it’s ecosystem. 

We explored the cave chamber for a few hours. The air reeked of decay, and mildew. The eerie screeching sounds of cave swiftlets echoed throughout the cave. Our guide showed us the entrance to another chamber that according to him has not been fully explored. Supposedly it may continue for miles but because it is full of water and is very narrow in parts it can’t be fully explored.   

See video above of inside of cave

The Ascent to the Top
The exhilaration of being in the cave started to fade when I realized we didn’t have time to waste and it was almost time to ascend back to the top. Our guide had joked with us that the ascension would be terrifying. Evidently there is a bungee effect and the ascent is much slower than the descent. He volunteered me to go first since I was the heaviest in the group and would take the longest to pull up. He felt it was better for me to go alone. I re-connected to the rope, and as soon as the guide alerted the guys on top I was ready with his radio, I was off. The guys laughed as I started to rise that I was a human piñata bobbing up and down. 
Me being pulled to the top
The trip back up by myself was a true test of my fortitude. Unlike the descent, now I didn’t have anyone else next to me. I didn’t have my guide.  I didn’t even have a way to talk to anyone. The guide had the only radio and there would be no way for anyone to hear me or for me to hear them if anything went wrong. True to my guides words, as I was pulled up I spun in circles, and swung like a pendulum. The worst part was the bouncing effect that resulted from the pulling. There is no feeling like that of bouncing up and down on a rope when you are suspended thousand feet in the air and spinning. At times, I needed to close my eyes and count to 100 to avoid the dizziness of the spinning and to calm my mind. After 30 minutes or what seemed like 8 years, the lip of the cave grew closer and closer and as soon as the roots of trees were within an arms length, I grabbed on and I was determined to never let go of the ground again until I was completely out of the cave. At the top, I stood up as one of the men who pulled me up helped me out of my harness and I immediately collapsed on the ground. Now that I was safe and at the top, I felt what seemed like a tsunami of relief crashing over me.  

Click the Video above of the Ascent/View from Rope While Hanging a thousand feet in the air

Cave Sotano Del Cepilles
Giant Stalagmite at Bottom of Sotano Del Cepiiles Cave
During the next morning, we drove to another cave, Sotano Del Cepilles, this one necessitated only a 900 foot abseil. This cave was down a dirt road passed the indigenous village of Aquismon. We parked near an agricultural field and walked passed some elderly indigenous women wearing traditional dress. 

The entrance, a hole into the 900 foot below us was surrounded by trees and much smaller than the entrance to the Cave of the Swallows. There were no rules governing this cave like with the Cave of the Swallows. Here, we could use mechanical devices to raise us from the cave. Our guides decided to use a motorcycle. We hired some nearby villagers with a motorbike. We would be lowered into the cave by the local village men and brought back up to the entrance by attaching our ropes to the motorcycle. One man would drive the motorcycle down the hill from the cave entrance, pulling us the whole 900 feet up to the top in a blistering speed, while another man would watch us to make alert the bike driver when to stop. Any number of things could have gone wrong but this is a running theme for this kind of trip. 

We forgot our walkie talkies, so when we went down to the bottom of the cave, we had no means to communicate with the top, other than to yank on the rope to alert them that we were ready to ascend. 

The descent was easy after the much scarier and deeper one in cave of the Swallows. The bottom of this cave was much more magical than Cave of the Swallows. The formations were more mazing. There was a lake and stalagmites the size of houses. We spend a few hours exploring the cave and then it was time to ascend. 

My Friends Posing Near a Cave Lake

 We went up in groups of two. Our waist harnesses were connected to the rope by a carabiner and our cave guide would tug on the rope to alert the top to pull the two up by motorcycle. As soon as he pulled, the two would be yanked upwards. One of my friends was standing to close to a loop created by the ropes slack, and their feet were pulled right out from beneath them sending them falling to the ground. 

Villagers Pulling Us Up 900 Feet by Motorcycle from Bottom of Cave

The ascent of 900 feet took approx. 1 minute with the motorcycle, much faster than the 45 minute ascent in cave of the Swallows. The difference was with such speed in the scent of this cave, the spinning on the top was relentless. The motorcycle would pull you within 30 feet of the top of the cave and then stop leaving you violently spinning in the darkness and on the verge of puking.

I had to close my eyes. The spinning continued for a few minutes while the crew on top transferred the ropes from the motorcycle to the manual pullers, who would then finish pulling you up to the top. 

White Water Rafting Down the Tampaon River
Tampaon River Rafting
The weekend was action packed, with little sleep and lots of adventure so far but when we found out that we could squeeze in an afternoon 6 hour white water rafting trip down the Tampaon River into a jungle clad gorge and stop to explore river caves and cliff jump along the way, and to top it off end the trip in an indigenous village with a feast of traditional Huasteca food before taking a taxi to our hotel for the night in Tampico, we couldn’t refuse. 

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