Sometime in the 14th century, the first Mexica found their way into the valley of Teotihuacán. The Mexica (often incorrectly called Aztecs in modern times) were new to the region. An aggressive, ambitious people from the north, they were fast becoming the dominant force in highland Mexico, conquering territory and setting up the powerful city of Tenochtitlán, which would soon rule a massive empire from what is now called Mexico City. Imagine that first search party—bold, feeling invincible as a nascent superpower—coming into a lush green expanse surrounded by rolling hills. The warriors are following tales told by the local Toltec tribes of a place in the mountains, just 25 miles from their new home, where the gods once lived. Then, turning a bend, their bravado gives way to awe as the home of the gods looms into view. Ruins of pyramids as high as 20 stories—so big they are initially mistaken for hills—line a huge road. Everywhere the explorers look lie crumbling temples, marketplaces and relics of a long-dead civilization with no name, no writing, no history. Just a vast city, once glorious beyond imagination, now abandoned.

The Mexica eventually patterned Tenochtitlán after this ghost of a city and turned the ruins into a sort of summer retreat for the elite. They named that ancient road the Avenue of the Dead and the two biggest pyramids the Pyramids of the Sun and Moon. The old city itself they called Teotihuacán—the place where gods are born.

Some 200 years later, in 1521, Spanish conquistadors toppled the Mexica's empire. And for hundreds of years Teotihuacán rested in gentle decay. When archaeologists first began excavating the site in earnest in the early 1900s, they had no better idea of who built the place than the Mexica had. Many thought it was a minor settlement erected by scattered tribes that were later subsumed by invaders. Today scholars know that Teotihuacán is actually much older and much more important than any of those early investigators could have guessed. It was the heart of an extensive empire that predates all the highland civilizations in the region and that reached as many as 700 miles away. A city that rivaled, and perhaps even dominated, the mighty Maya kingdoms in Guatemala and Honduras.

But with no written texts to guide them, archaeologists have long been puzzled about how the people of Teotihuacán lived. By tunneling into the monuments and carefully excavating the smaller structures nearby, they have been able to sketch out some answers. They now envisage a verdant, multiethnic community with rich social strata, including merchants, traders and artisans from across Mexico.

Less clear is what Teotihuacán's politics were. Two schools of thoughts have emerged. One sees a city ruled by a warlike king, unchallenged and infallible, who guided a strict state with an iron fist. The other envisions a mercantile state in which several powerful families vied for influence but could not wrest supreme control and therefore played a careful political game. Now two projects are racing to settle the debate and solve the puzzle. One thing is agreed on, though: in the end, Teotihuacán was not a place where gods were born but a place where men built them out of blood and stone—and a place where they eventually dashed them to the ground.

An Elusive King
Reconstructing the politics of a bygone culture is no easy task. Picture landing in Washington, D.C., 1,400 years after its collapse and trying to understand its people. Did they worship Abraham Lincoln? Were they a military state? Did they conduct elaborate rituals in the reflecting pool? Which of their rulers or priests lived atop the Washington Monument? These are the kinds of questions that Saburo Sugiyama of Aichi Prefectural University in Japan has asked about Teotihuacán for more than 35 years.

Three major structures dominate the site: the Sun Pyramid is the tallest, the Moon Pyramid is the second tallest and the terminus of the Avenue of the Dead, and the smallest, on the same side of the avenue as the Sun Pyramid, is the Temple of the Feathered Serpent. (This last temple is often called Quetzalcoatl, after the similar-looking Mexica god that was probably inspired by this older version.) Although the Feathered Serpent structure is smaller than the others, many have suggested that it was the most significant and housed potent kings or priests. Located at the very center of the original city, it is made up of two pyramids, surrounded by a squat walled complex.

In 1989 Sugiyama and archaeologist Ruben Cabrera Castro of Mexico's National Institute of Anthropology and History unearthed a crucial new clue to the story of Teotihuacán: 18 bodies near the temple that had been ritually sacrificed and laid out. Soon after, the research duo found more such bodies and then, while tunneling under the temple, still more—well over 100 in all. The individuals they recovered, mostly male, seemed to be warriors from other lands, suggesting a martial society in which rule was enforced at the tip of an obsidian blade.

Sugiyama began to construct a highly specific idea of what kind of place Teotihuacán was in its heyday. He envisioned an ironfisted king who ruled with unquestioned authority in the city. “This city was created, materialized with power. You can't just suggest your ideas by saying, ‘Hey, guys, let's make some buildings,’” he says. “You need to convince people with power.”

Just outside of Teotihuacán, in a small town, Sugiyama is sitting in his laboratory. The building contains more than two million objects found during the decades since he started excavating. He has a quiet, thoughtful demeanor in person, and it is easy to picture him as the vagabond hippie he was in the 1970s, leaving his native Japan to travel the world. But when it comes to archaeology, few are as ambitious and driven.

In 1998, frustrated that he had not found a tomb or other direct evidence of his kings, Sugiyama decided to tunnel under the giant Moon Pyramid in search of them. It was an ambitious project, but it offered the best way to understand the power structure of the society and was a good place to search for a tomb. Like any big city, Teotihuacán was built in stages. Anthropologists think that starting in 150 b.c., various factions coalesced around this spot in a lush valley and formed an alliance of sorts. They built their city in spurts, first here, then there. Sugiyama's tunneling revealed that the Moon Pyramid was one of the first big structures they created, in a.d. 100.

But they did not erect it all at once. From 1998 to 2004, Sugiyama tunneled past seven previous versions, built one over the other, like Russian dolls. The fourth version—built early in the third century a.d., according to carbon dating—was a major upgrade from the previous one. This was a time of growth and perhaps even the birth of an empire.

Although Sugiyama had yet to locate his kings, his discoveries fit neatly into an emerging picture of Teotihuacán's rise to power. Whether behind a king's banner or not, as Teotihuacán built up its city, it started reaching out its fingers. Some 450 miles southeast of Teotihuacán, in what is now Chiapas, lie the ruins of a small city called Los Horcones that emerged at around the same time. Even this far away from Teotihuacán, Claudia Garcia–Des Lauriers of California State Polytechnic University, Pomona, who has excavated the site, sees its definitive imprint: “The fact that you lay out your main plaza area for your entire community to kind of echo the way that one walks down the Avenue of the Dead and enters into a large open plaza—that's really powerful. You are trying to invoke [Teotihuacán].”

The similarities are subtle but noticeable to a trained eye, Garcia–Des Lauriers says. Given its layout and the style of its pottery, Los Horcones was either a military outpost or a close trading partner with Teotihuacán. Interestingly, the road Garcia–Des Lauriers suspects to be impersonating the Avenue of the Dead does not lead anywhere—it abruptly ends at a large boulder. Yet the dead end makes sense if people who had traveled to the parent city were trying to create a miniature version of it. “This is really just like Mecca in Islamic societies,” Sugiyama says of Teotihuacán. “It would have seen pilgrimages.”

Similar cities have been discovered in recent years all over Mexico. Scientists now believe that Teotihuacán controlled a region far more vast than any had expected before those ruins came to light—covering much of modern southern Mexico and stretching into Honduras. As its domain expanded, goods such as limestone and feathers poured in from the far reaches of the Mesoamerican world. In fact, in the jungle to the east, controlled by the legendary Maya kings, scientists have found references to a mysterious mountain city to the west, where the people were as thick as reeds in a marsh. Many suspect this western place was Teotihuacán, which apparently even exerted control over the Maya megacity of Tikal in Guatemala. Evidence from another Maya city, Copán in Honduras, suggests that a person from Teotihuacán assassinated its king and established his own rule.

Such an empire, Sugiyama says, needed a strong, charismatic king. He envisions one such leader living around a.d. 219, watching over monumental construction projects and ushering in an empire that would last 500 years.

Eventually, inside the fourth version of the Moon Pyramid, Sugiyama found a stamp of that empire—remains of 12 humans (most likely captives) and more than 50 animals, including wolves, jaguars and eagles, arranged in an elaborate configuration. The layout now looks to be a representation of a creation myth, with a cluster of knives in a circle like a sundial pointing north. “Again, we found very strong evidence of the state—decapitations, knives,” he says. “Again, we didn't find the body of a ruler.”

In ancient Maya cities, almost every building of note contains a king under the front steps or in the building itself, elegantly preserved and attended by jars of precious spices and stones. Yet to date, not a single king has been discovered in Teotihuacán.

Monarchy or Corporate Society?
Despite the missing king, Sugiyama is still convinced that Teotihuacán was a monarchy, like ancient Egypt, complete with a godlike head and a military apparatus focused on keeping its multiethnic citizens in line. But other experts take a different view. “You cannot have a multiethnic society ruled by one person. They would have had coups d'état all the time,” insists archaeologist Linda R. Manzanilla of the National Autonomous University of Mexico. “Teotihuacán had a corporate society, which is the opposite of what the Maya had.”

Based on her own excavations, Manzanilla argues that Teotihuacán was ruled not by a supreme leader but four powerful houses, all vying for dominion like something out of Game of Thrones. If Sugiyama's version of Teotihuacán is like Egypt, think of Manzanilla's as a little like the Roman Republic—a mighty state ruled by committee. Kings in Teotihuacán were figureheads controlled by the ruling classes from four houses, which were represented in the iconography of Teotihuacán: coyote, feathered serpent, jaguar and eagle. Each house dominated a quadrant of the city and sent representatives to a central governing building with an administrative section for each house. The feathered serpent and jaguar were the strongest houses; thus, the most ornate temples—the Pyramid of the Sun and the Feathered Serpent Temple—were on their side of the Avenue of the Dead.

Both Manzanilla's and Sugiyama's camps say the other's claims are baseless. How can two people study the same site for decades and come back with totally different conclusions? Partly, it may be that Manzanilla looks at Teotihuacán through a very different lens. Where Sugiyama has spent his career looking at the Teotihuacán equivalent of the Washington Monument, Manzanilla says she has been digging up Georgetown: her picture of Teotihuacán stems from her work over the past 20 years in the everyday homes of its people. In the 1990s Manzanilla excavated Oztoyahualco, an artisan apartment compound in the northwest of the city—an area she thinks was controlled by the house of the eagle. Unlike Maya apartment complexes, which have just one shrine, this compound had many different shrines from different traditions. For Manzanilla, this multiethnic quality defines Teotihuacán. She sees a place that could thrive only because wealthy landowners from abroad controlled trade corridors and the goods that fed the community's rapid growth. With so many powerful factions, it would have been very hard for a lone tyrant to hold the population under his thumb. When the city banded together in 150 b.c., Manzanilla says, one group would not have had a monopoly on resources as some of the Maya rulers had. She reasons that the rulers of Teotihuacán relied on taxes from the provinces to build their empire. As such, each shareholder would have leverage in the use of that power. Those with control over the richest territories, such as the Feathered Serpent Temple, had the most leverage over decisions.

This kind of forced power sharing is rare in the ancient world but not unheard of. Rome and Greece were, of course, republics for many years. Likewise Mohenjo Daro, an ancient city in Pakistan's Indus Valley in 2000 b.c., seems to have shared power with a settlement called Harappa, and Tiwanaku in Bolivia shared power with Wari to the north until a.d. 1000.

Sharing with another city you cannot defeat is different than sharing within a city, however. Manzanilla admits that most ancient civilizations had a single ruler and that the setup she proposes is a little odd. She believes, though, that in any given region, some cultures are bound to experiment with joint rule. Yet the strongest evidence she has to support her idea is not something she found but rather something she did not find. Something no one has found.

“Where is that powerful king depicted? Where is he buried? Where is his palace? Can you imagine a site like Teotihuacán, with 125,000 people, [having] a single ruler? His living place and his burial place should have been outstanding. No doubt. And we don't see that,” she says. “You'd see him in the vessels, in the throne, in the stelae, in the palaces themselves.”

What she does see is a four-petaled flower inscribed throughout the city. Historian Alfredo López Austin of the National Autonomous University of Mexico says that this symbol may represent the four houses that ruled the city. Like Rome, such a place would have been rife with plotting and power plays. As Teotihuacán expanded and its influence spread, the elites acquired increasingly more control. Markets were paved and expensive limestone began appearing throughout the city. The elites of all four houses became greedy and competitive.

To some extent, the data back up this scenario. Increasingly, scientists have been finding that people throughout Mexico moved to the city but maintained their ethnic heritage for hundreds of years. Just as New York City has Spanish Harlem and Chinatown, Teotihuacán had districts for people from Oaxaca to the south, for the Maya and for those from the corridor connecting to the Gulf of Mexico. For example, take the neighborhood of Teopancazco, just south of the Temple of the Feathered Serpent. In the early part of this century, Manzanilla excavated the site, which was dominated by elites from along the trade route to what is now Veracruz, east of Mexico City, and whose symbol she thinks was the feathered serpent. With such a lucrative territory, they would have controlled massive wealth and thus might have sponsored the nearby temple for their feathery emblem.

Manzanilla's work showed that these feathered serpent elites dined on 12 different fish species, salted and smoked, from their home along the Gulf of Mexico, 130 miles away, and decorated their clothing with gulf seashells. “There was a competition between elites to show the best of cosmetics, pigments, hides, cotton clothes, attire, headdresses,” she says.

Nowhere was this competition more blatant than in the burials. Since 2005 Manzanilla has painstakingly analyzed several fascinating graves of elite adolescents at Teopancazco. The children are decorated in elaborate fashion, with cinnabar, greenstone and mica from around the empire, plus lots of material imported from their home region.

The wealthy lived in increasingly lavish style for centuries, building up their palaces and lining them with stones that had to be transported from miles away. But the high life could not last forever. In a.d. 350 something snapped. Twenty-nine elites seemed to have been decapitated, and their heads were adorned in a manner only found in the ancient Veracruz region. Manzanilla suspects this was a “termination” ritual, denoting some kind of cultural transformation. At this time, the Feathered Serpent Temple was replaced by one in front of it that displayed jaguars, like an artist redoing a sketch. In fact, after this point, few if any feathered serpents appear anywhere in the city, a sign that the Veracruz people no longer held much sway, in Manzanilla's view.

But they were not gone. After that, a new line of elites must have ascended, and it appears that they continued to prosper in Teopancazco for two more centuries. Then, in a.d. 550, the city of Teotihuacán burned. No one knows why. Manzanilla says that there is no sign of an invading force. What is in evidence is a large gap between the rich and poor. Analysis of human remains from the site indicates that many of the wealthy were healthy, whereas the poor were malnourished, had back problems from carrying heavy loads and even suffered conditions caused by lack of sunlight—perhaps from slaving away in some workshop. “My guess is that the intermediate elites revolted against the ruling elites,” she says. “The ruling elite tried to control this movement too late. These people already had a lot of interests, a lot of alliances in the corridors, and they revolted.”

After that, Manzanilla theorizes, a contrite leadership focused its building effort on housing across Teotihuacán and not on elaborate temples. Another century or so more, and the city collapsed for good. For the elites, she says, this sequence of events would have meant simply picking up and returning to their homelands in the corners of the empire.

Teopancazco reveals a slice of life from Teotihuacán separate from the grand temples. The city was diverse, but it was not a melting pot. Instead it was a patchwork, with each culture keeping its identity and operating in fierce competition with its neighbors for prestige and authority. This patchwork may explain why there was no uniform written language or images of kings as there was for the Maya. Such representation would have meant tilting the scales too far in one side's favor.

Perhaps the most fascinating aspect of Teotihuacán archaeology is that both Manzanilla's and Sugiyama's theories could be true. George Cowgill, an emeritus professor at Arizona State University, has proposed that Teotihuacán vacillated between both models, occasionally switching when the right ruler grabbed power. Neither Manzanilla nor Sugiyama likes this compromise, however.

Chamber of Secrets
Archaeologists might never know who ruled Teotihuacán for sure. But very soon Sergio Gómez Chávez may find a crucial piece of the puzzle. Gómez Chávez, an archaeologist at the National Institute of Anthropology and History, has been digging at Teotihuacán for decades, both in common people's homes, such as the city's Oaxaca neighborhood, and in the grand temples. That work included an excavation of the Temple of the Feathered Serpent's drainage system in an effort to restore it to protect the structure from further water damage during storms. It turns out the ancient drainage system works perfectly. But Gómez Chávez found that it was purposefully stuffed up with 50 bodies missing arms and legs. Who builds a drain only to ceremonially plug it? Gómez Chávez knew that the blocking of the drain occurred around the same time that the fourth version of the Moon Temple was built. What if it was done on purpose? What if the city's denizens wanted to flood the area every year, like the reflecting pool in Washington, D.C. (the people of Teotihuacán were known to divert rivers, among other waterworks projects)? It was during one such flooding episode, on a fateful Thursday in October 2003, that the archaeologist made his most shocking discovery.

“I'm coming in to work like any normal day, and [workers] inform me that a big hole has formed” near the temple, Gómez Chávez recalls. He rushed to the site, and sure enough the rain from the night before had opened a perfectly circular tunnel going straight down into blackness. He did not hesitate. He told one of the workers to find a rope. Though not a skilled mountaineer, he managed to tie himself to the rope, and several workers lowered him into the hole, hand over hand. The hole—a foot or two wider than his shoulders—went down some 50 feet and stopped. It was almost like a well except when Gómez Chávez got to the bottom, he found that the dirt and rock on either side was loose, as if it was put there to seal a horizontal tunnel going in both directions. At the top of that fill was a gap that he could almost peer through. “I couldn't sleep for a week, because you don't know what's in it,” he recollects.

It seemed that a straight, horizontal tunnel, perpendicular to the shaft, had long ago been filled in with stones and dirt to seal it forever. One end went to a ceremonial entrance behind him, long hidden from view. The other, Gómez Chávez soon learned, continued beyond view—straight to the heart of the Feathered Serpent Temple. The hole he had found was perhaps for ventilation or for light or a view of the stars. Without it, the tunnel may have stayed secret forever. Thus began a 10-year effort to clear the tunnel and find what it hid. The tunnel was filled around that crucial third-century era of expansion. Using radar and sonar, Gómez Chávez learned that it led to a series of three chambers under the center of the pyramid. So he carved his way toward them, one foot at a time. Today he is almost at the end.

A few months ago Gómez Chávez invited me to see the tunnel. Now I am here at his site at the foot of the Temple of the Feathered Serpent, in the wide expanse that he believes was once allowed to flood every year. Walking along the tunnel, I am struck by how chilly it is. It is a hot autumn day outside, but down here it is moist and cool. Gómez Chávez says that when the people of Teotihuacán used this tunnel, the water table was right at their feet. This, he guesses, might have been the reason they put the tunnel at this height. A cold, dark place with water along the ground might have represented the underworld. In several places, I see remnants of a special clay they used to line the tunnel. Peppered with sparkly pyrite, the clay looks almost like twinkling stars. “This is no longer a temple dedicated to Quetzalcoatl but a temple to commemorate the beginning of mythic time,” he reflects.

So far Gómez Chávez and his colleagues have removed almost 1,000 tons of filler from the tunnel. In so doing, he has found sealed compartments, one after the other, which he has opened to expose ever more elaborate offerings, including masks, weapons, even reed mats that would have functioned like thrones. “The concentration of materials—it's just amazing. It's unbelievable the things that he is finding,” Sugiyama says. Now empty, the compartments appear as pits lining the tunnel floor. Walking on wood planks, I have to be careful not to slip into one.

In the spring of 2013, using a robotic drone, Gómez Chávez reached two of the three major chambers at the end of the tunnel. One contains dozens of quartz spheres, the other pyrite mirrors. No one has any idea what they were or has seen anything like them. Standing by those chambers, I squat and try to peer ahead at the last chamber, still sealed. It is a few feet lower than where I am. “It's very wet down there,” Gómez Chávez says. “With all the mud and water, we have had to go slowly now.”

Gómez Chávez imagines this place as an elaborate ritual site, where men left the earthly world for a moment and emerged as kings. Sugiyama, slightly irritated that he did not find the tunnel during his own investigation, says there is no better candidate for a royal tomb. Even Manzanilla admits that the discovery of a royal tomb would be a big deal for Teotihuacán. She insists it will not hurt her theory, but that depends on what is inside.

Meanwhile Manzanilla is excavating her own site, called Xalla, looking for a smoking gun. A series of five structures not far from the Sun Pyramid are arranged in a diamond shape, almost like a four-petaled flower with a shrine in the middle. This, she thinks, is the administrative center of the city, where each of the four houses sent emissaries to look after their business.

Either way—whether Manzanilla proves her theory of distributed power or Gómez Chávez discovers an all-powerful king buried at the end of the tunnel—Teotihuacán will never be the same. At long last, the lives of its people, like ships coming out of the fog, are slowly emerging from 1,300 years of mystery to tell their story.