The Great Maya Aquifer

Exploring the Hidden World Beneath the Yucatán Peninsula

The Yucatán Peninsula in southeast Mexico is home to an extraordinary network of caves and sinkholes that have influenced human activity for thousands of years. Recent explorations by the Great Maya Aquifer project are uncovering fascinating insights into this submerged world, shedding new light on ancient civilizations and prehistoric life.

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. [Image: Ricardo Castillo]

Cenotes: Sacred Wells of the Maya

The Spanish invaders of Mexico adopted the term “cenotes” from the Maya word tz’onot, referring to natural sinkholes filled with fresh water. These cenotes were crucial for Maya settlements, providing a vital source of drinking water in a region with scarce surface water.

Beyond their practical importance, cenotes held deep spiritual significance for the Maya. The Sacred Cenote at Chichén Itzá, for example, was linked to the city’s Great Plaza by a ceremonial path.

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. [Image: Karla Ortega]

Historical records by Franciscan bishop Diego de Landa describe how the Maya made offerings to the gods by throwing precious artifacts—and even human sacrifices—into the cenote. 20th-century explorations confirmed these accounts, revealing human remains, jade, gold, pottery, and wooden idols at the bottom of the well.

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A Vast Subterranean Realm

While cenotes provide visible access to underground water, they are merely gateways to a much larger subterranean network. The Great Maya Aquifer project has mapped over 1,650 km of these caves, with Sac Actun—also known as the White Cave—stretching more than 350 km.

Seen from underwater, the cenotes resemble windows opening into the immensity of the Great Maya Aquifer. [Image: Pedro Almada]

Guillermo de Anda, director of the project, describes these caves as “the last frontier of exploration of pristine places left in the world, apart from the oceans.” The vastness of the system, combined with its unique environment, makes it a challenging but rewarding space to study. The submerged conditions have preserved organic materials like textiles, charcoal, and even human remains, offering rare archaeological insights.

A Changing Landscape: From Dry Caves to Water Reservoirs

Surprisingly, these caves were not always underwater. During the Ice Age, the Yucatán caves remained dry, creating a dramatically different environment for early humans and animals. As sea levels rose about 11,000 years ago, increased rainfall seeped into the porous bedrock, gradually submerging the caves. Today, they act as massive natural cisterns, storing rainwater and supplying fresh water to the region.

Prehistoric Discoveries: Bears, Mammoths, and Sabre-Tooth Tigers

The submerged caves have preserved evidence of prehistoric life in the region. One of the most unexpected finds was the discovery of five bear skulls, which puzzled researchers since bears were not previously believed to have lived in the area. Other prehistoric remains include gomphotheres (early relatives of elephants), mammoths, and sabre-tooth tigers.

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. [Image: Guillermo Pruneda]

The presence of human remains dating back 13,000 years further deepens the mystery of early human habitation. The careful placement of bear skulls in specific locations suggests that people may have used these caves for ritualistic purposes rather than as permanent shelters.

Caves as Sacred Spaces: Tracing Early Religious Practices

De Anda believes that caves played a significant role in ancient religious practices, a pattern seen in multiple cultures worldwide. Sites like Altamira in Spain, known for its Palaeolithic cave art, provide strong evidence that early humans viewed caves as magical or sacred spaces. While it is uncertain whether the Maya directly descended from these early settlers, both cultures demonstrated a spiritual connection to the underworld.

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

The Future of Exploration

Despite decades of study, much of the Yucatán’s underground world remains unexplored. The Great Maya Aquifer project continues to uncover new artifacts and expand our understanding of ancient civilizations. With modern diving technology and archaeological research. This hidden world beneath the Yucatán Peninsula continues to reveal its secrets. Providing invaluable insights into human history and the natural world.