Who built Teotihuacan? The city, the pyramids, the tunnel of mercury and the theories

Architecture · 4 September 2026

Teotihuacan was built by a people whose name we do not know, between about 100 BC and AD 250, in the Valley of Mexico 25 miles (40 km) northeast of today's Mexico City. It was not the Aztecs, who arrived a thousand years after the city was abandoned and gave it the name we use, "the place where the gods were made"; and it was not the Maya, who lived 600 miles away, although the two civilizations traded and fought. At its height around AD 400 Teotihuacan held 100,000 to 125,000 people on eight square miles of planned streets, the largest city in the Americas and one of the largest in the world, with the third-largest pyramid on Earth at its centre. Below: what the excavations have established about its builders, the three great monuments, the tunnel discovered in 2003, the city's fall, and a separate section for the theories.

The people: what is known

The builders left no readable writing, so archaeology and later sources have to speak for them. Three things are solid. First, they came from the Valley of Mexico itself: pottery and villages in the valley run continuously from 500 BC into the city's early phases, and a volcanic eruption around 50 BC that buried the rival town of Cuicuilco to the south probably sent refugees north to the growing settlement at Teotihuacan. Second, the city was multi-ethnic: excavated neighbourhoods include a Oaxaca barrio with Zapotec tombs and pottery, a merchants' quarter with Gulf Coast and Maya wares, and isotope studies of teeth show that a large share of residents were born elsewhere. Third, it was ruled without kings, or at least without the cult of them: unlike the Maya, Teotihuacan shows no royal portraits, no named rulers, no dynastic monuments, and its art favours goggle-eyed rain gods, feathered serpents and processions of identical figures. Most archaeologists now think it was governed by a council or collective elite. The language spoken is unknown; Nahuatl, Totonac and Otomi have all been proposed. Teotihuacan overview.

The plan

The city was laid out on a grid oriented 15.5 degrees east of north, an alignment repeated in every building and probably tied to the sunset on the days the sun passes overhead. The spine is the Avenue of the Dead, a road 1.5 miles (2.5 km) long and 130 feet (40 m) wide, which the Aztecs named because they took the platforms along it for tombs. At its north end stands the Pyramid of the Moon, in the middle the Pyramid of the Sun, at the south the Ciudadela with the Temple of the Feathered Serpent. Around them lay about 2,000 apartment compounds, single-storey walled complexes of rooms around courtyards housing 60 to 100 people each, with drains, plastered floors and painted walls: the earliest apartment housing in the Americas.

The Pyramid of the Sun

The Pyramid of the Sun was built in one effort around AD 200: about 730 feet (225 m) on each side and 216 feet (66 m) high, roughly a million cubic metres of rubble and adobe faced with stone and once plastered and painted red. It is the third-largest pyramid in the world by volume after Cholula and Khufu's. It was raised over a cave, artificially enlarged into a four-lobed chamber, which is probably why the spot was chosen: caves were places of origin in Mesoamerican belief. Excavations in 2011 found offerings at the base and near the top, including obsidian, greenstone masks and a figure of the fire god; nothing like a tomb has been found.

The Temple of the Feathered Serpent and its sacrifices

The Temple of the Feathered Serpent, in the walled Ciudadela, is smaller but the most revealing building in the city. Its facade carries stone heads of the feathered serpent alternating with a goggled, scaly creature, probably a headdress of the war or time god. Excavations in the 1980s found more than 200 people buried around and beneath it in groups, young men in warrior costume with their hands tied behind their backs, women, and a central burial of twenty, sacrificed at its dedication around AD 200. Isotopes show many came from outside the city. Later the facade was deliberately covered by a new platform and the temple's images defaced, an act read as a political revolt around AD 300 that ended whatever regime had built it.

The tunnel of mercury

In 2003 a rainstorm opened a sinkhole in front of the Temple of the Feathered Serpent, and the archaeologist Sergio Gómez found a tunnel about 330 feet (100 m) long running 60 feet (18 m) below the temple, sealed since about AD 250. Over the next fifteen years his team removed 1,000 tons of fill by hand and robot and recovered some 75,000 objects: greenstone statues, jaguar remains, seashells from both oceans, rubber balls, pyrite mirrors, and, at the end, three chambers. The tunnel walls were dusted with pyrite so that torchlight made them sparkle like stars, and the floor of the last section held pools of liquid mercury, an image of the underworld rivers. No royal tomb was found; the tunnel appears to have been a model of the cosmos beneath the temple, used for rituals and then closed. The temple and the tunnel.

The Pyramid of the Moon

The Pyramid of the Moon closes the north end of the avenue and echoes the outline of Cerro Gordo, the mountain behind it. Tunnelling by Saburo Sugiyama's team between 1998 and 2004 showed it was built in seven stages from about AD 100, each larger pyramid wrapping the last, and found dedicatory burials inside: bound captives, and animals, pumas, wolves, eagles and rattlesnakes, some buried alive in cages, with obsidian blades and greenstone figures. The plaza in front held about 100,000 people, the whole population of the city.

Why it fell

Around AD 550 the ceremonial centre burned. The fire was selective: temples and elite compounds along the avenue were destroyed and their sculptures smashed, while ordinary neighbourhoods were untouched, which points to an uprising from inside rather than an invasion. The city had already been shrinking; drought, deforestation of the valley for lime plaster and firewood, and the rise of rival centres are all suspected. By AD 650 the population was a fraction of its peak, and the rest of the site was quarried and farmed. The Aztecs, arriving in the 1300s, held the ruins sacred, buried their rulers' offerings there and told that the gods had gathered at Teotihuacan to create the sun of the present age.

Versions and theories

Everything below is a version, not a fact. These are the claims that appear in search next to "who built Teotihuacan", with who made each and what the evidence says.

The Aztecs built it

Version. The most common assumption, because the site is in Aztec country and carries an Aztec name. Reply. The Aztecs entered the Valley of Mexico around AD 1250, seven centuries after the city was abandoned; they told the Spanish they had found it in ruins. Their own capital, Tenochtitlan, lies under Mexico City.

The Maya built it

Version. Because the Maya are the best-known pyramid builders of Mesoamerica. Reply. Teotihuacan predates the classic Maya cities and its architecture, art and burial customs are different. The two did meet: in AD 378 a Teotihuacan-linked lord named Siyaj K'ak' arrived at Tikal and installed a new dynasty, an event recorded on Maya stelae, and Teotihuacan-style buildings appear at Tikal and Copán. Influence went both ways.

Toltecs, Olmecs or Totonacs

Version. Colonial sources credited the Toltecs; some modern writers the Olmecs or Totonacs. Reply. The Toltec capital Tula was founded after Teotihuacan fell; the Olmec heartland on the Gulf was in decline centuries before the city rose. The Totonac claim is a modern tradition without archaeological support, although Gulf Coast people certainly lived in the city.

The pyramids encode the solar system

Version. The layout of the three pyramids supposedly matches the orbits of the planets, or Orion's Belt, as claimed for Giza. Reply. The grid is astronomically aligned, to the sunset on the zenith passage days and to the Pleiades, which is well documented; the planetary and Orion readings require choosing which buildings count and ignoring the rest of the city.

Aliens and a lost civilization

Version. The mercury in the tunnel and the size of the Pyramid of the Sun are offered as proof of advanced technology. Reply. Mercury was produced across Mesoamerica from cinnabar, the red pigment used on the pyramids and in tombs; it has been found in Maya burials too. The pyramid is rubble and adobe faced with stone, built by a city of 100,000 whose houses, kitchens, workshops and rubbish have all been excavated.

What is in the archive

The three monuments, the Pyramid of the Sun, the Pyramid of the Moon and the Temple of the Feathered Serpent, are in the Ancient temples of the world collection beside the other American pyramids: Cholula, the largest in the world by volume, El Castillo at Chichen Itza, Tikal and the Templo Mayor of the Aztecs. For the Egyptian comparison see how the pyramids were built.

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