Above The Great Maya Aquifer project is dedicated to understanding and preserving the submerged world beneath the Yucatán Peninsula. Diving is an indispensable tool for their research and conservation work.

The Great Maya Aquifer: exploring a hidden world beneath the Yucatán Peninsula

Southeast Mexico is rich in caves. This extraordinary underworld has influenced human activity for thousands of years. Now a project dedicated to understanding and preserving this realm is shedding new light on the archaeology of the Yucatán Peninsula, as Guillermo de Anda told Matthew Symonds.

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The Spanish invaders of Mexico called them cenotes. This came from a mishearing of the Maya word tz’onot, which was used to describe great circular sinkholes that dropped down to inviting pools of freshwater. In a region where groundwater is scarce, these natural wells were a magnet for Maya settlements. As well as providing a vital source of drinking water, the cenotes were woven into Maya beliefs. A fine example comes from the sprawling city of Chichén Itzá, which was carefully positioned to benefit from nearby cenotes. One of them, the Sacred Cenote, was connected to the Great Plaza at the heart of the city by a ceremonial way. A 16th-century Franciscan bishop, Diego de Landa, recorded that a range of offerings were made there: ‘into this well they have had… the custom of throwing men alive as a sacrifice to the gods, in times of drought… They also threw into it a great many other things, like precious stones and things that they prized.’ Sure enough, investigation of the cenote in the 20th century revealed human remains, and a wealth of artefacts, including wooden idols, pottery, jade, and ornate gold discs.

The Great Maya Aquifer project is dedicated to understanding and preserving the submerged world beneath the Yucatán Peninsula. Diving is an indispensable tool for their research and conservation work. PHOTO: Karla Ortega.

Cenotes are created when the ground surface collapses into underground cavities, exposing the water table below. While the size of these natural wells can be impressive, with the Sacred Cenote measuring about 60m in diameter, this pales by comparison with the wider expanse of caves lying beneath the Yucatán Peninsula. This natural network is still being explored and charted, so its full extent remains unknown. Even so, it is clear that the scale of this underground realm is nothing short of extraordinary. Recent work by the Great Maya Aquifer project has revealed that one cave system, known as the Sac Actun or White Cave, stretches for over 350km. This project is dedicated to learning more about all aspects of this breathtaking submerged world. While the water within it remains essential for the modern inhabitants of the Yucatán, these sunken passages also hold evidence for thousands of years of human activity in the area. The project’s work is revealing not only fascinating new glimpses of Maya life, but also the world inhabited by some of the earliest human occupants of what is now Mexico.

Final frontier

‘I always say that this is the last frontier of exploration of pristine places left in the world, apart from the oceans,’ says Guillermo de Anda, director of the Great Maya Aquifer project. ‘That is one way of getting across how important this area is. It is an amazing experience to work there – completely magical – because it is like a planet within a planet. As much of the cave system is submerged, it is a place where you need special equipment, special training, and a special attitude to be able to explore it. In some ways it is like an astronaut going to outer space, but in our case we are charting an inner space. And it is an inner space that is so vast that there is still plenty underneath the ground waiting to be discovered and documented. Putting together everything that has been mapped so far gives us 1,650km of caves.’

left The research team of the Great Maya Aquifer project carries out archaeological prospecting using non-intrusive technology in the Sacred Cenote at Chichén Itzá, more than 50 years after the last exploration in this body of water was carried out by Román Piña Chan.
The research team of the Great Maya Aquifer project carries out archaeological prospecting using non-intrusive technology in the Sacred Cenote at Chichén Itzá, more than 50 years after the last exploration in this body of water was carried out by Román Piña Chan. PHOTO: Karla Ortega.

‘People have been working on this for a long time. I started as a cave-diving apprentice 40 years ago. Back then, I don’t think anyone appreciated how big the network would turn out to be, that four decades later people would still be mapping and exploring it. Even after all of this time, the archaeological finds don’t cease to amaze us. One reason for this is because we find things that we don’t get on the surface. What I mean by that is the level of preservation is amazing. We have found textiles, wool, charcoal, and even human remains. Together, they have changed our perception of the archaeology of this area.’

The water that enchants modern visitors to the cenotes and was so important to Maya success is also a key reason why charting the caves is such a laborious process. Limited access points, the length of some cave systems, and the lack of natural light all make pushing the boundaries of knowledge in this environment a highly specialised pursuit, where safety is paramount. Given that the presence of water seems quintessential to both the beauty of the caves and the challenge they present for modern survey, it can be surprising to learn that they were not always submerged. On the contrary, the first human settlers in the region were greeted with a radically different underworld. Back then, towards the end of the last Ice Age, the caves were still dry. While this would have made interacting with them a very different experience, the subterranean labyrinth still had a powerful pull on human imagination and belief.

Above Seen from underwater, the cenotes resemble windows opening into the immensity of the Great Maya Aquifer.
Seen from underwater, the cenotes resemble windows opening into the immensity of the Great Maya Aquifer. PHOTO: Pedro Almada.

‘In one cave we were lucky enough to find what turned out to be the first of five skulls,’ says Guillermo. ‘The first time I saw the skull, I wondered what kind of animal it was from. Initially I thought it might be a big jaguar, or feline of some kind. When we got a photograph, I contacted my zooarchaeologist friend Chris Götz. I remember that I was back in my house that evening when he replied and said something like “This is not from Yucatán, this is a picture from somewhere else – you are trying to trick me!” So I said, “No, no, it was taken this morning”, but it was only when he saw another photograph with one of my colleagues diving close to the skull that he believed it was from Yucatán. And the reason why he suspected a trick, is because the skull was from a bear. Before we found it, we had no clue that bears existed nearby. You do get Pleistocene bears in north Mexico, but after that there appeared to be a gap as far as Belize. Now that gap seems to be filling in.’

LEFT A portion of a Maya skull is recorded by the Great Maya Aquifer project team in the depths of a cenote in Quintana Roo.
A portion of a Maya skull is recorded by the Great Maya Aquifer project team in the depths of a cenote in Quintana Roo. PHOTO: Rodrigo Friscione.

‘Our five bear skulls belonged to two adults and three subadults, but one of the weird things was that there were no long bones associated with them. This led us to suppose that the bears didn’t die there accidentally. Instead, the heads – and only the heads – had been deliberately placed there. Unsurprisingly, this opened a huge line of research questions. Previously, only a few Pleistocene animals were known from the area. But now, thanks to projects like the Great Maya Aquifer project, we can say that there were gomphothere – an early relative of the elephant – and mammoth, as well as sabre-tooth tigers. We also have the remains of humans that were in the region 13,000 years ago, and maybe even earlier. That brings us back to the question of the bear skulls.’

‘I have always thought that in ancient cultures – and Mesoamerica is no exception – religion started in caves. Just look at places like Altamira, in Spain, with its amazing Palaeolithic art. That really looks like a ritualistic approach to caves. We can see signs that people believed these places had a magical and religious significance, and were powerful for that reason. Although we cannot yet prove it, my working theory is that early humans living in the Americas were worshipping in caves. If so, this is a historical process that we can trace through to the Maya – although I should stress that I am not saying the Maya can definitely be traced back directly to those first settlers. This is something that is still the subject of polemic debate! But I do believe that we can see evidence of a ritualistic mindset among those Ice Age humans interacting with the caves. Of course, they could find shelter there, so maybe they lived there for short periods of time, but we have not found much evidence for that, and the caves didn’t present very comfortable conditions. Instead, what we have seen so far seems a better fit with caves being viewed as marginal, magical places.’

LEFT This Ice Age bear skull is among the most important findings made by Guillermo de Anda. It was found in a cenote in the Yucatán.
This Ice Age bear skull is among the most important findings made by Guillermo de Anda. It was found in a cenote in the Yucatán. PHOTO: Guillermo Pruneda.

It was at the end of the Ice Age, about 11,000 years ago, that the caves took what is now their familiar form. This was a time of rising sea level, but it was not only salt water that inundated the caves. Instead, increased rainfall seeped through the porous bedrock, draining into the expanse of natural underground passages. While this water does eventually make its way to the sea, the caves should not be seen as underground rivers. Instead, they are essentially gigantic cisterns that fill up during the rainy season. As a result, droughts were capable of producing severe fluctuations in the water level of these natural reservoirs.

ABOVE An aerial view of the Sacred Cenote in Chichén Itzá. It was connected to the Great Plaza by a causeway.
An aerial view of the Sacred Cenote in Chichén Itzá. It was connected to the Great Plaza by a causeway. PHOTO: Chris Millbern.

Water world

‘The Maya civilisation generally stretches back about 3,000 years in this area,’ says Guillermo. ‘And the caves and cenotes presented a resource that the Maya knew how to use perfectly. Back in the 1930s there was an archaeologist called Sylvanus Morley, who was an amazing scholar – they talk about him being a spy, too, but he was a great archaeologist. He said that wherever you get a Maya settlement in the northern lowlands – that is the area the Yucatán is in – you will find a cenote nearby, to provide a water source. Today, we know that these cenotes had a symbolic meaning as well. So, for the Maya, the cenotes had a double function: as water sources and as powerful magical places. Because of that, it was desirable to live near them.’

RIGHT Corey Jaskolski, Great Maya Aquifer team technology specialist and National Geographic Society Explorer, undertakes photogrammetry of Cenote Holtún, which lies to the west of El Castillo at Chichén Itzá.
Corey Jaskolski, Great Maya Aquifer team technology specialist and National Geographic Society Explorer, undertakes photogrammetry of Cenote Holtún, which lies to the west of El Castillo at Chichén Itzá. PHOTO: Karla Ortega.

One of the finest examples of the importance of cenotes in the Maya world is the city of Chichén Itzá. There, the extraordinary offerings made at the Sacred Cenote are far from being the only testimony to the significance of these natural wells. Instead, they seem to have exerted a powerful influence on the urban architecture. A remarkable example of this can be found on the Great Plaza at the heart of the city. Various monuments were erected in this space, including an impressive ball court, where teams could compete in this important sporting and religious event. The most-imposing monument, though, is a great pyramid temple, which the Spanish named ‘El Castillo’ or ‘the castle’. Bishop Landa recorded that this was dedicated to the worship of K’uk’ulkan, a great feathered snake.

LEFT El Castillo at Chichén Itzá. This remarkable stepped pyramid lies at the intersection of two lines drawn between cenotes lying to the north and south, and to the east and west. Recent geophysical survey suggests another cenote lies under the structure.
El Castillo at Chichén Itzá. This remarkable stepped pyramid lies at the intersection of two lines drawn between cenotes lying to the north and south, and to the east and west. Recent geophysical survey suggests another cenote lies under the structure. PHOTO: Eberdova, Dreamstime.

‘El Castillo is placed centrally between the four cenotes,’ says Guillermo. ‘To the north lies the Sacred Cenote; to the south, Xtolok Cenote; east is Kanjuyum; and west is Holtún. If you trace two lines between the north and south and east and west cenotes, you will find that El Castillo lies at the exact point where these alignments intersect. About five years ago, one of our colleagues, Dr René Chávez Segura, used geophysics to discover what appears to be a cenote under El Castillo. No one has yet been able to get inside this to check the results on the ground, but, if they are correct, it is very important. In terms of the Maya world-view, it would also make a lot of sense.’

ABOVE A Maya offering in Balank’anche Cave, also known as the Cave of the Jaguar God. It lies within the archaeological zone of Chichén Itzá.
A Maya offering in Balank’anche Cave, also known as the Cave of the Jaguar God. It lies within the archaeological zone of Chichén Itzá. PHOTO: Karla Ortega.

‘When we think about directions today, we imagine north, south, east, and west. The Maya, saw these instead as the colours white, red, black, and yellow. But they also saw a fifth direction: the centre. This sacred direction lay at the centre of space, and the Maya built their religion and lives around it. The centre was extremely significant as a source of both extremely good and extremely bad things. It was also associated with a colour, a fine blueish-green: the same colour as the cenotes. We have to imagine the Maya taking the five cenotes into account when this part of the city was built. What they seem to be doing is bringing together both the cenotes and the urban architecture to create a physical expression of the Maya world-view. Our next step is to get into this fifth cenote and prove that it exists. As archaeologists, we need to go there.’

right The most recent explorations by Guillermo de Anda and his team in the Balank’anche Cave have yielded discoveries such as this underwater tripod vessel, which had not previously been recorded.
The most recent explorations by Guillermo de Anda and his team in the Balank’anche Cave have yielded discoveries such as this underwater tripod vessel, which had not previously been recorded. PHOTO: Chris Millbern.

Subterranean city

A cenote under El Castillo would not be the only indication that underground features were judged significant by the inhabitants of Chichén Itzá. ‘Caves are important to understanding the site,’ says Guillermo. ‘One, at Balank’anche is about 4km from Chichén Itzá and might give us the earliest date for the city, while another, at Balamku, potentially allows us to witness the last moments during the demise of the city. Both caves contain amazing numbers of artefacts. Balank’anche was excavated back in 1958 by E Wyllys Andrews IV, Willie Folan, and George Stuart. Back then, caves were not seen as that important for archaeology in general, but the work was very well done. Almost 100 incense burners – some ceramic and some made of stone – were found in the cave. One thing that surprised the archaeologists was that a number of these incense burner bore the face of the rain god Tlaloc. Now, Tlaloc was a central Mexican deity, rather than a local one, raising questions about the nature of the link between that area and Chichén Itzá.’

‘We went back to Balank’anche and were able to secure a charcoal sample. That gave us a radiocarbon date of over 2,000 years ago, which in Maya terms takes us into the Late Preclassic era. It also provides a very early concrete date for activity at Chichén Itzá. Back in the 1950s, the cave was seen as something that was nearby the city, but detached from it. If we approach this as landscape archaeologists, though, we can see it formed part of the wider complex. That is an important difference in perception. There is also a physical link between the cave and the city. A sakbe – that is, a causeway resembling a road – was built running all of the way to Balank’anche. These causeways had a ceremonial purpose, and one of the ways in which they were used was to connect sites to a city, in order to make them part of that city. So our Late Preclassic date from Balank’anche is important for understanding Chichén Itzá, as it is one of the earliest secure dates – perhaps the very earliest secure date – for occupation of the city.’

righT Guillermo de Anda in front of one of the seven Maya offerings documented in Balamku Cave, a 1,000-year-old Mayan sanctuary located in Chichén Itzá (TOP). Here we see one of those offerings, which consists of dozens of incense burners, vessels, plates, and metates, among other archaeological elements (BOTTOM). All remain in an amazing state of preservation.
Guillermo de Anda in front of one of the seven Maya offerings documented in Balamku Cave, a 1,000-year-old Mayan sanctuary located in Chichén Itzá (above). Here we see one of those offerings, which consists of dozens of incense burners, vessels, plates, and metates, among other archaeological elements (below). All remain in an amazing state of preservation. PHOTO: Karla Ortega.
PHOTO: Karla Ortega.

‘Our second cave, Balamku, is only about 1.5km from Balank’anche. It is surprising that these two sites are so close together. We are wondering if they were paired in some way, but this is still under investigation. Balamku is extraordinary. It is a beautiful cave, but very hard to get into. Inside, there is an amazing array of artefacts. So far, we have found seven places where offerings were made, along a stretch of nearly 700m of cave that we have been able to map. Most of the artefacts we have discovered are incense burners – almost 200 of them – and there are also some jaguar pots. The incense burners still contain the remains of whatever was being presented to the gods. It looks like these offerings were burnt during ceremonies that took place inside the cave.’

‘To us, it is amazing that the Maya were able to reach so far into Balamku. It is mostly dry, but we have spotted water at the end of it: there is a cenote that we still need to explore. Today, we still have to use special equipment in the cave, because there is very little oxygen, so you get fatigued quickly. The passage is also low, so you have to crawl most of the way. That means we have to imagine the Maya holding the offerings – and carrying them carefully to avoid breaking anything – while grasping a torch in their other hand, and moving through this difficult space. It’s an amazing effort. Perhaps that speaks of a time of crisis, but if so, it was prolonged. Two random charcoal samples that we took from the burners have revealed that this cave was being used for at least 200 years.That date range might suggest Balamku was used for repeated special ceremonies rather than during a single crisis.’

above Constant dripping over hundreds of years has allowed the concretion of some elements deposited in Balamku Cave, such as this Tlaloc incense burner.
Constant dripping over hundreds of years has allowed the concretion of some elements deposited in Balamku Cave, such as this Tlaloc incense burner. PHOTO: Karla Ortega.

Once again, a number of the incense burners bear the face of Tlaloc, the rain god more closely associated with the Aztecs and the Toltecs than the Maya. Perhaps, then, these offerings were being made at times of drought, when the water level in the cenotes was dropping. Whatever the motive, it still leaves open the question of why a distant deity was so popular at Chichén Itzá. ‘In the past, they used to talk about an invasion from Central Mexico,’ Guillermo observes. ‘But there’s no proof of that, and today we think it looks more like an influence. So rather than a war, perhaps we should be thinking of agreements between these states. Even so, the presence of Tlaloc remains surprising. After all, Chichén Itzá is a really important Maya site, and the sacred heart of this site are its caves. So why would you put what is effectively a foreign god at the heart of the Maya area? This is something that is still a source of great debate.’

below & Inset El Osario, or the Tomb of the Great Priest, is a stepped pyramid that lies to the south-west of El Castillo at Chichén Itzá. The monument was built on top of a natural cave. Here, biologist Arturo Bayona is next to the access hole to a second cave below El Osario.
below & Inset El Osario, or the Tomb of the Great Priest, is a stepped pyramid that lies to the south-west of El Castillo at Chichén Itzá. The monument was built on top of a natural cave. Here, biologist Arturo Bayona is next to the access hole to a second cave below El Osario. PHOTO: Karla Ortega.
PHOTO: Karla Ortega.

A further example of a connection between city architecture and subterranean space can be found at El Osario. This is another step pyramid at Chichén Itzá, albeit a smaller one than El Castillo. It holds an important place in the history of the city, as it was believed to be the last monument built there, on the strength of a Maya text bearing a date of AD 998. El Osario was built over a cave just like – it now seems – El Castillo. When the project examined El Osario, they were able to recover charcoal from the underlying cave. This gave a radiocarbon date that was 200 years earlier than the supposed foundation date for the stepped pyramid, meaning that the first phases of the structure are probably earlier than El Castillo. It certainly looks as though El Osario developed in stages. First of all, there was the natural cave, which was enhanced when a platform was built over it, allowing people to enter the subterranean space and perform ceremonies there. It was only in a later era that the structure evolved into the step pyramid we can see today.

Underground, overground

right The registration, protection, and study of submerged cultural heritage are all objectives of the Great Maya Aquifer project. Here a diver is examining a Maya pot.
The registration, protection, and study of submerged cultural heritage are all objectives of the Great Maya Aquifer project. Here a diver is examining a Maya pot. PHOTO: Ricardo Castillo.

El Osario, then, offers another elegant illustration of how influential the underworld beneath Chichén Itzá could be on the structures visible above ground level. Thanks to the efforts of the Great Maya Aquifer project, the opportunities that the underworld of the Yucatán presented for human activity can now be followed in ever greater detail over a period of at least 13,000 years. From those first settlers, greeted with dry caves that offered shelter and a focus for belief, via the rise of great Maya cities, through to the modern inhabitants of the peninsula, the caves have nourished a wealth of human needs. Happily, the waters within them have not only provided a source of hydration and spiritual sustenance, but also proved ideal for preserving extraordinary archaeological material. We can be certain that they still hold plenty of secrets to share.

FURTHER INFORMATION
For more information about the Great Maya Aquifer project, see the website https://granacuiferomaya.org/.

CWA is grateful to Guillermo de Anda.