Few of the modern visitors to Teotihuacan are aware of the vast and mysterious underworld of caves and man-made tunnels that extends under much of the ancient site and for miles around. The existence of these tunnels has been known for centuries, but not even the most recent research has been able to solve the mystery of their origin and purpose. Very much like at Giza, in Egypt, these tunnels are rumored to connect all the main pyramids by means of underground passageways, and perhaps even lead to the records of a lost civilization.
The French explorer and anthropologist Desiré Charnay was among the first Europeans to penetrate into this labyrinth of tunnels in modern times, and leave a detailed account of it. In his 1880 book “ Les anciennes villes du Nouveau Monde ”, Charnay recounts having been led by his guide to some cavernous quarries, two-and-a-half miles (1.6 kilometers) west of the Pyramid of the Moon. There he was showed the entrances to several galleries, branching off in different directions at regular angles. These led to different chambers, which he described as “large halls”, one in particular “shaped like a rotunda” and filled with human remains. Charnay had no doubt that these tunnels had been dug in ancient times, and he speculated these could have served as quarries to build the many structures above ground in Teotihuacan, and were only later turned into catacombs. Charnay followed another tunnel for a distance of almost one kilometer (0.62 miles), without approaching its end. The tunnel never deviated from its course and appeared to point in the direction of the Pyramid of the Sun, almost two kilometers (1.2 miles) further to the south-east. Interestingly, these tunnels seemed to be partially dug into the volcanic conglomerate that covers the entire valley to a depth of several meters, and part into the much harder bedrock.
A local legend collected by Peter Tompkins in his “ Mysteries of the Mexican Pyramids ”, has one of these caves running on a straight line to Amecameca, some 65 km (40 miles) to the south-east. The existence of these subterranean caves was certainly well known to bandits and revolutionaries during the 1800s and early 1900s, as many of them allegedly took refuge in the caves at the time.
Quarries and just quarries?
Geologists believe that this set of cavities originated millions of years ago, when intense volcanic activity in the area left a network of “ lava tubes ” and bubble-shaped caves, some as much as 20 meters (65.6 feet) high and up to 100 meters (328 feet) in length. The ancient inhabitants of Teotihuacan certainly enlarged and expanded these natural cavities as a source of construction material. Millions of tons of volcanic rocks were extracted from these tunnels, although it is unclear why the ancient Teotihuacanos would not have chosen the much more accessible deposits above ground. Rather, they chose to dig a maze of tunnels in the near complete darkness, under constant threat of cave-ins and floods.
Already over the course of the 1950s, French-American archaeologist René Millon speculated that the largest pyramids could have been built on top of vast underground cavities. Digging under the Pyramid of the Sun, he found evidence of a huge blocked pit, which he believed could lead to a tomb “of immense proportions.” It was not until 1971, however, that excavations revealed the entrance to an ancient tunnel underneath the pyramid. The passage ran in an easterly direction for about 100 meters (328 feet), until a system of chambers arranged in the shape of a four-leaf clover, very near the center of the pyramid. The tunnel appeared to have been deliberately blocked and sealed in antiquity, but the chambers were found to be completely empty except for a few smaller obsidian artifacts and pottery fragments. No trace of the “huge pit” reported by Millon was found.
Over the course of the 1990s and early 2000s, archaeologist Linda Manzanilla of the Autonomous University of Mexico led a comprehensive examination of the caves and tunnels under Teotihuacan. She reached the conclusion that the vast majority of the tunnels accessible today were man-made, and not natural lava tubes. She suggested they had most likely originated as quarries, but were later used for a number of funerary and ritualistic purposes.
Descending into the Underworld
In the early months of 2017 I was able to personally explore a section of the tunnels located less than a few hundred meters to the east of the Pyramid of the Sun. Most of the entrances and side passages have been blocked in modern times, but it is still possible to follow their course for a short distance.
Some more tunnels branch out from a vast chamber resting on rough rock-cut columns or pillars. One of those can be followed for a distance of perhaps 50 or 60 meters (164 – 196 feet) until a pit from where more passageways branch out. The loose conglomerate that forms the walls and ceiling of the tunnels and chambers does not encourage further exploration for the risk of cave-ins. Even in their present dilapidated condition, the tunnels follow a regular plan with fairly constant height and width. It is possible that some of the deeper tunnels continue under the much harder basalt bedrock, as the ones visited and described by Charnay in 1880. The existing tunnel entrances could thus represent an attempt by later occupants of the site to penetrate a much deeper and perhaps far older labyrinth.
Rivers of Mercury
For the inhabitants of Teotihuacan, the labyrinthine network of caves and tunnels under the city represented the entrance to the Underworld. In the Codex Xolotl , the glyph used to represent Teotihuacan contains the depiction of two pyramids above a cave with a person inside. This suggests a possible connection with the Aztec traditions of Chicomoztoc, the “ Place of the seven caves ”, from which the present humanity was said to have emerged after a previous world was destroyed.
In 2003, the entrance to a previously unknown tunnel was discovered under the pyramid of Quetzalcoatl. The tunnel ran about 100 meters (328 feet), and had been intentionally sealed with large boulders in antiquity. Archaeologist Sergio Gomez has since described the tunnel as “one of the most important discoveries in the history of Mexico”. The tunnel, with continued exploration, has since revealed over 50,000 artifacts. Particularly puzzling has been the discovery in 2013 of hundreds of metallic spheres, ranging from 4 to 12 cm (1.57 to 4.7 inches) across. The spheres appear to have been covered in pyrite, while a core of clay and other unidentified compounds.
At the end of the tunnel lies what is likely a system of three chambers, still awaiting exploration. In one of the chambers, vast quantities of liquid mercury were detected. Gomez speculates that these veritable “pools” of liquid mercury could have symbolized an underworld river or lake.
Traces of Immortality?
Many ancient civilizations, particularly the Chinese, considered mercury a vehicle for immortality. However, due to its high toxicity and complex extraction, the discovery of liquid mercury is extremely unusual at ancient sites, and is virtually unparalleled in Mesoamerica. If the caves and tunnels of Teotihuacan were designed as a symbolic representation of the Underworld, it is very well possible that the new tunnels recently discovered under the pyramid of the feathered serpents could one day lead to a mythical tomb, perhaps the final resting place of mysterious ruling elite responsible for the construction of Teotihuacan and for the monumental megalithic architecture present at the site.
It is equally possible that the exploration of some of the other tunnel systems to the East of the Pyramid of the Sun and to the West of the Pyramid of the Moon, including the ones entered by Charnay and never again explored, would lead to similar discoveries. Very much like at Giza, these tunnels could lead to some sort of Mesoamerican equivalent to an ancient “ Hall of Records ”, whose discovery could finally help to shed light on the origins of Teotihuacan and its “ Gods”.