Any time you have looked at vacation pictures featuring Mexico, El Castillo is certainly not something you could have missed. It is a magnificent structure made of stone, resembling an almost perfect pyramid, standing out among other buildings in Chichén Itzá, the Maya site in Mexico. People all around the globe have been coming here for ages to admire this amazing building from the outside, fascinated by its beautiful symmetrical composition. Almost everyone knows it for its spectacular effects during the day, when the sun makes it resemble a large snake crawling down the steps of the temple.
However, when a team of geophysicists looks deep down through the bedrock, they find that the most surprising thing about the pyramid is not what lies above it but rather what lies directly beneath its foundation. In the layers below the dense stone pavilion, there lies a large subterranean water-filled cavern named a cenote. This newly found natural structure provides new insight into the rationale behind the construction of this world wonder in this particular location.
A pyramid within a pyramidThe uniqueness of this structure becomes clear once you look beyond its outer shell. Even before geophysical research, archaeologists had already discovered something unique about El Castillo. As per the history mentioned on the website of the
Chichen Itza Pyramid, this structure is actually composed of several structural nesting dolls.
Archaeologists who began excavations on the interior found that the pyramid itself was constructed upon at least two smaller and older pyramids, making this site one that is consistently renovated and layered. Each generation of the culture enclosed the sacred chambers of its ancestors inside a more elaborate shell. As intriguing as the architecture was, the finding of the underground water cave made the mystery even more profound by moving the intrigue from horizontal to vertical dimensions. Clearly, the structure served a dual purpose: the construction of a passage linking the underworld to the heavens.

Geophysicists have discovered a large, water-filled cavern, or cenote, directly beneath El Castillo at Chichén Itzá. This finding, revealed through electrical resistivity imaging, offers new insight into the pyramid's construction and its symbolic connection to the Maya underworld, Xibalba. Image Credit: Wikimedia Commons
Map of the secret underground chamber beneath the stoneThe excavation of such a huge cave underneath a thick and ancient temple required some of the most sophisticated tools ever invented. Scientists did not have the luxury of digging up and through the temple's floor in search of a natural cavity; hence, they resorted to high-tech solutions.
The breakthrough came in a comprehensive geophysical study titled
Karst Detection Beneath the Pyramid of El Castillo, Chichen Itza, Mexico, by Non-Invasive ERT-3D Methods published by
Scientific Reports. Researchers used electrical resistivity imaging to send safe electrical currents into the ground. By measuring how the currents moved through the earth, they mapped a significant karst cavity filled with water directly under the pyramid.
The ancient Maya people saw a lot more meaning in the cenote than merely using it for a practical purpose like obtaining water in a land scarce of water sources. To them, the deep sinkholes filled with water were very significant portals to the mythical underworld Xibalba. They were thus forming a symbolic connection by deliberately positioning their pyramid in the centre of an underground water cave. The pyramid itself represented a point of alignment between the three worlds: heaven, the earthly realm where humans lived and the spiritual underworld beneath them.