For archaeologists and tourists alike, the monumental ruins of Mesoamerica are humbling testimony to the complex civilizations that once flourished there. Even the names of these peoples evoke power and mystery: Aztecs, Maya, Zapotecs, Toltecs, Olmecs. But of all the great pre-Columbian metropolises that dot the region, arguably the most magnificent of all belonged to a people who remain nameless. The Aztecs, who took over the area some 25 miles north of modern Mexico City in the 15^th century, were convinced it was built by supernatural beings. Their name for the city, which we still use: Teotihuacán, or Place of the Gods.

With few clues to guide modern scientists, the origin and fate of the ancient rulers of Teotihuacán are a mystery to this day. But thanks to a discovery made this fall by an international research team, that mystery may finally be starting to unravel. In mid-October, archaeologists stumbled across a burial chamber deep inside Teotihuacán's massive Pyramid of the Moon. Inside they found a skeleton and more than 150 artifacts probably dating to about A.D. 150. It is, exults anthropologist Michael Spence of the University of Western Ontario, "a fantastic find."

Until the 1960s, no one realized that Teotihuacán's great Avenue of the Dead, anchored at its northern end by the Pyramid of the Moon and flanked by the even larger Pyramid of the Sun and other ceremonial buildings, was the core of a much larger metropolis. Indeed, at 8 sq. mi. and with an estimated population of 150,000, Teotihuacán was the largest city in Mesoamerica in its heyday (about A.D. 500) and one of the six largest in the world-larger even than Rome. Its political power reached all the way to Mayan city-states hundreds of miles away, with outposts as far away as Guatemala.

Unlike its Mayan counterparts, though, Teotihuacán has yielded very few inscriptions, and those are in a hieroglyphic language that archaeologists have not yet been able to decipher. The city's celebrated painted murals don't provide many clues either. "There are very few glimpses of daily life," complains Arizona State University anthropologist George Cowgill. The best information scientists have to date comes from a series of mass graves discovered about a decade ago in the so-called Feathered Serpent Pyramid by Cowgill, his Arizona State colleague Saburo Sugiyama and Rubén Cabrera of Mexico's National Institute of Anthropology and History. Most of the 150 skeletons found there were buried with their hands and feet bound, suggesting that they had been sacrificed; most of them were also dressed as soldiers and armed with obsidian-tipped spears and other weapons. More sacrificial victims were discovered within the Pyramid of the Sun by another team. But these finds raised as many questions as they answered about the culture of Teotihuacán.

Then, last year, Sugiyama and Cabrera decided to tackle the Pyramid of the Moon. Like most Mesoamerican pyramids, this one was built like an onion. Explains Cowgill: "They would build a small pyramid, then build a larger one over it and then build a third one after that." As a result, the interior is almost solid dirt and rubble, with no distinct passageways. This makes the going slow and expensive. It took the archaeologists 3½ months to reach the burial chamber, which is about 90 ft. inside the pyramid.

It was worth the trouble. "No one has ever found a burial of this richness intact at Teotihuacán before," says Cowgill. Among the booty: two 1½-ft.-high greenstone statuettes; a couple of larger human figurines fashioned from obsidian; at least 15 double-edged obsidian knives similar to those used in sacrifices; shell pendants in the form of human teeth; pyrite disks (which served as mirrors); the skeletons of two young felines (possibly jaguars) in the remnants of a wooden cage; and the scattered bones of at least seven large birds.

But it's the human bones that have Spence's attention. Once they have been fully extricated, he will try to determine the individual's age and gender (probably male). He'll also look for evidence of disease, malnutrition or developmental abnormalities as well as wounds, broken limbs or signs of hard labor and such status symbols as a deliberately shaped head or filed teeth. The absence of lavish body ornaments, the position of the skeleton's hand (which was belatedly found behind its back, as if the arms had been tied) and the location of the burial chamber all suggest to Sugiyama that the individual was bound and sacrificed. "We thought [the skeleton] might be a ruler or a person of high status, but it may not turn out to be that," he cautions.

In the long run, the scientists say, the individual's social status and the richness of the offerings may not be as important as the burial's age, which places it in a crucial time period only a couple of centuries after the city was founded. "We know almost nothing about Teotihuacán's early political history, so [this discovery] should shed a lot more light on that," says Cowgill.

But the real key to unraveling the secrets of Teotihuacán is more digging--a lot more--and Sugiyama's team is still hard at work. Despite this impressive discovery, says Cowgill, "95% of the city is still unexcavated. We're just scratching the surface." -Reported by Andrea Dorfman/ New York