Exploring the Tunnel Underneath the Feathered Serpent Temple at Teotihuacan, Mexico

In 2003, we started an ambitious program of investigation and conservation of the Ciudadela complex, one of the most important and largest architectural complexes at ancient Teotihuacan. The Temple of the Feathered Serpent had suffered severe damage for several years, so we had an obligation to ensure its preservation. In order to answer many remaining questions about Teotihuacan and to conserve its buildings, we spent several seasons excavating various spaces that are part of this important and unique complex. Our project has also developed a new explanatory paradigm that differs in some ways from what other authors have proposed in terms of the function, use, and characteristics of the occupation of the space where the Ciudadela complex was constructed.

Our explorations in the large plaza have provided information about the process of occupation at the Ciudadela. Based on systematic stratigraphic excavations, we know that the Ciudadela was constructed in an area that was originally used as farmland. Later during the Tzacualli and Miccaotli phases(1-200 C.E.), this space was occupied by several structures that were part of a first sanctuary, which was subsequently destroyed by Teotihuacanos to build the majestic complex that stands today.

Below the large esplanade, Julie Gazzola discovered and explored the remains of several structures that predate the construction of the Ciudadela. The characteristics of these structures suggest that they were occupied by groups with high social status and most likely were part of an important first sanctuary built there. One of the structures is over 120 meters long and has features that suggest it may have been used as a structure for playing ballgames. Other structures contain mural paintings, temples, altars, large courtyards, and rooms. The orientations of these buildings differ by three, five and sometimes more than thirty degrees from the Teotihuacan standard orientation, which is 15° 17” east of north. This result is surprising, and it is changing previous ideas about the orientation of the city and its urban development.

Evidence from excavation also confirms that the plaza of the Ciudadela was designed and built to be flooded with water in order to form a reflective surface. This “water mirror” was a metaphorical representation of the Primordial Sea, from which, in times immemorial, the Sacred Mountain emerged at the beginning of time. This information supports the idea that the Ciudadela was used in the performance of rituals and the enactment of myths alluding to the original creation and maintenance of the universe, as well as those related to the renewal of life.

In 2003, during conservation work on buildings in the architectural complex, we made a surprising discovery in front of the steps of the platform attached to the Feathered Serpent Temple. Heavy rains prior to the discovery caused a depression in the ground that revealed a deep hole .83 m in diameter. With the help of a rope and several workers, I was lowered down almost 14 meters through a small hollow. At the bottom, I realized that there was an underground conduit oriented to the east toward the Temple of the Feathered Serpent and to the west toward the center of the great plaza.

The tunnel was completely filled, most likely by the Teotihuacanos, with an impressive volume of earth and carved stone blocks. These materials lined the subterranean duct on both sides and prevented access to the interior. I knew without a doubt that the exploration of this underground conduit would require planning and careful design of an excavation strategy, as well as sufficient financial resources to ensure the development of the research.

In 2004, 2005, and 2010, we used Ground Penetrating Radar (GPR) to establish that the tunnel was likely between 100 – 120 meters in length, with its east end located at the center of the Temple of the Feathered Serpent. The register of anomalies suggested the possibility of large chambers, one in the middle and another of even larger size at the terminus of the tunnel.

For the exploration of the tunnel, we established a series of theoretical considerations and assumptions. First, that the city of Teotihuacan was an embodiment of the divine act of production that ordered the Cosmos into three vertical levels (the celestial region, the earthly plane, and the Underworld) and the horizontal plane into the cardinal directions, with their limits representing the ends or corners of the world. The city was, for the Teotihuacanos, a replica of their own concept of the Universe.

Second, that the Pyramid of the Feathered Serpent represented the "Holy Mountain." Besides being the axis mundi, this mountain was the axis that allowed communication between the three vertical levels of the Cosmos and between the horizontal directions of the Universe. It was also the "First True Mountain" emerging from the Primordial Sea, marking the start of mythical time, the count of days, and the calendar.

Third, that below the Primordial Mountain was the Sacred Cave, which represented the entrance and road to the Underworld. It was a place full of riches and nurturing seeds, inhabited by deities and creative forces responsible for maintaining order in the Universe. Thus, the tunnel must be a symbolic representation of the Underworld.

Fourth, that according to Mesoamerican cosmology, the Underworld has its own sacred geography.

Fifth, that the main entrance of the tunnel was always located to the west. According to various sources and myths, the entrance to the Underworld, named by Central Mexican and Maya peoples as Tlalocan, Mictlan, or Xibalba–the place of the dead–was in the west, further associating the tunnel with the concept of the Underworld.

Finally, a sixth premise considered the underground passage as the site of multiple and continuous intrusions for performing ritual acts of divine investiture for power legitimization. We postulated that we should find the remains of those persons receiving or transmitting charges and gifts, as well as some objects used in these rituals, in the tunnel.

When I obtained permits and funding to explore the nature of the tunnel in 2010, I organized a team of specialists and workers. We focused our exploration in an area where we predicted that the main entrance to the tunnel might be located. The excavations began in an area of approximately 100 square meters. At a little more than 2 meters below the surface, we discovered a pit in the tuff that measured almost 5 square meters. After several months of work, we finally found the access to an underground conduit, confirming our hypothesis that we should expect to find the tunnel entrance in this location.

In order to improve our planning strategy for the investigations, we used different technological resources—such as a laser scanner used to record and survey everything with millimeter accuracy—to plan our work. During a primary test in 2010, the laser signal could pass 37 meters through a small hole, and in 2011 reaches 73 meters, confirming our predictions based on GPR data that there was a long tunnel leading toward the pyramid.

The first pictures of the inside of the tunnel were obtained by a small remote-controlled robot that we constructed and equipped with video cameras. This robot could penetrate 37 meters into the tunnel and allowed us to assess the conditions and stability. In 2013, we tested a second robot built by a student of the National Polytechnic. The robot was equipped with an infrared camera and a miniature laser scanner. This robot managed to penetrate the last thirty meters of the tunnel.

Along the tunnel, we discovered more than twenty thick walls that originally blocked access to the tunnel. These walls were partially destroyed by the Teotihuacanos when they deposited or removed things from inside the chambers. The fact that they had subsequently filled the entire tunnel made us assume that this incursion was intended to deposit something very important at the end of the tunnel. Either way, we were sure that we were the first to enter the tunnel for about 1,800 years, and that the passage had not been looted or altered during this period.

In 2013, the excavation reached 65 meters into the tunnel, confirming the existence of two side chambers whose walls and roof were likely finished with the application of a powder of metallic minerals (such as pyrite, hematite and magnetite). The chambers surely shone with torchlight, creating an effect like the starry night sky or sparkling running water. In the southern antechamber, we discovered more than 400 mineral metal balls, something never before seen in any archaeological excavation. After the two side chambers, the tunnel descended an additional three meters below the surface and continued for at least 35 meters farther to the east. At the end of the tunnel, we found three chambers facing north, south and east, corroborating previous radar information.

As of 2015, our explorations have reached depths of 13 to17 meters below the surface, uncovered 103 meters of tunnel length, and resulted in the removal of about 1000 tons of earth and stones. We have recovered and recorded more than 75 000 objects that we are studying, classifying, and restoring.

Our research has distinguished itself by the collaboration of specialists in different disciplines and institutions, both Mexican and foreign. The study of animal bones and botanical remains is carried out in the Archaeozoology and Archaeobotanical Laboratories of the branch Laboratories and Academic Support of INAH. Archaeozoologists have identified the remains of thousands of waterfowl, big cats, sea shells, and even wings of beetles. Archaeobotanists have identified more than 15,000 different plant seeds, pollen, and phytoliths.

During the excavation process, we recovered thousands of objects made of jade, serpentine and other green stones, malachite, argillite, amazonite, turquoise, slate, obsidian, rock crystal, and liquid mercury as well as hundreds of circular plates and pyrite mirrors. We found four extraordinary green stone anthropomorphic sculptures, hundreds of large shells—some inscribed and others made into musical instruments—rubber balls, necklaces of shell, jade and pyrite, and hundreds of pottery vessels without traces of use. We have also recovered fragments of human skin and over 4,000 objects and fragments of wood that are still in good condition.

We conducted non-destructive testing of inorganic materials for identification of trace elements. Analysis (PIXE) of green stones and other minerals has taken place in the Laboratories for Research and Conservation of the French Museums (Louvre).

We have performed radiocarbon dating on organic materials such as wood and bone in the Laboratory on Accelerated Mass Spectrometry in National University, in Mexico City. We have conducted infrared and Raman Spectroscopy analysis of organic materials such as rubber and amber at the Center of Applied Physics and Technology.

Geological studies have confirmed that the Teotihuacanos constructed the tunnel at a depth that was below the natural water table in order to recreate the watery conditions of the Underworld. The last thirty meters of the tunnel are even deeper to ensure that this part of the tunnel would always contain a pool of water, representing the sacred water of the underworld. According to myths, the Underworld has its own sacred geography. In the Underworld, there are rivers and lakes connected with the sea, just as there are mountains and a sky with their own stars.

In conclusion, we postulate that ritualized political acts were performed in the Ciudadela complex. Rulers acquired divine investiture that was assumed by or passed on to their successors. Ritual acts were used as propaganda and political justification.

The ritual and political activities carried out in this great scene gave legitimacy to the institutions of the state and dominant groups that held political and economic power in the city. The ritual, in its scope and significance, was the ideal communication medium in a complex system of relationships that shaped and gave meaning to social and collective thought.

The liturgical paraphernalia displayed in religious rituals and ritualized political acts served to maintain and reproduce the structures of power. The Feathered Serpent supplied the divine investiture to rulers legitimizing their power. For this reason, we believe that the main building of the Ciudadela had great significance, and that the ritual and political activities conducted in the sanctuary at the true center of the city represent both the axis of the Universe and serve as a representation of the Cosmos.

The Pyramid of the Feathered Serpent symbolized the Sacred Mountain, the union and the link between different levels and regions of the cosmos. The construction of artificial underground caves symbolically transformed terrestrial space and had a strong meaning related to myths about the creation of the Universe and humanity. The tunnel under the Temple of the Feathered Serpent represented the Underworld—a dark, cold and wet place—where elites delivered and acquired the power to govern.

For the Teotihuacanos, the Ciudadela was a place to get involved in a religious experience like no other because the sacred geography reproduced and recreated the work of the gods. Thus, through the ritual offerings, sacrifices, and murders that took place in this great primal scene, the Teotihuacanos were attempting to recreate the entrance to the Underworld.

We are confident that through a comprehensive study of the complex set of meanings associated with this place we will have the opportunity to understand the thoughts of the people who realized, perhaps like no others, the ethereal nature of their worldview.
 
Sergio Gómez Chávez

Mexican archaeologist, professor, and full-time researcher at the National Institute of Anthropology and History (INAH) since 1987. He has worked in Teotihuacan directing several research projects and organizing various academic events. He has published over 70 scientific articles on specialized craft production, farming systems, the foreign presence, and ethnic interaction. He has also published on aspects of the structure and organization of the urban area, the writing system, and the spoken language of ancient Teotihuacan. Additionally, he has published several essays on the protection of cultural heritage. Between 2004 and 2007 he studied for a PhD in anthropology at the National School of Anthropology and History in Mexico City. In 2005 and 2006 he held academic and research stays at the Sorbonne, Paris IV and the School of Higher Studies in Social Sciences in France. In 2006 he received the award for the best Teotihuacan research. Since 2002 he has served as director of the Citadel Project, an ambitious project dedicated to archaeological research and conservation of one of the three largest architectural complexes of Teotihuacan.

 ( Sergio Gómez Chávez    National Institute of Anthropology and History, Mexico）

（Source: Research Center for World Archaeology, Shanghai Academy）