Teotihuacan: The mysterious ancient city that continues to puzzle archaeologists

The city was founded sometime around 200 to 100 BCE and reached its height between 150 and 500 CE, when it supported a population estimated between 125,000 and 200,000, which made it one of the six largest urban centres in the world at the time.

During the centuries before the Common Era, Teotihuacan developed from a small village into a thriving settlement.

It expanded as migrants displaced by the eruption of the Xitle volcano, which likely occurred in the late 2nd or early 3rd century CE, arrived in the area.

They brought new agricultural methods, religious customs, and trade connections.

Farmers cultivated maize, beans, squash, and amaranth, supported by irrigation systems and terracing in the fertile valley.

Over time, the city became a major regional centre, where construction projects showed a high degree of political control, urban planning, and the distinct Talud-Tablero architectural style that would spread across Mesoamerica. 

Unlike many Mesoamerican civilisations, Teotihuacan did not appear to follow a dynastic system of kings.

No royal tombs or inscriptions naming individual rulers have been found, and artistic depictions avoided personal images.

According to many scholars, the city may have been governed by a council made up of elite families or representatives of powerful neighbourhoods, organised into barrios with distinct temples and possibly semi-independent leadership, though the exact structure is uncertain.

Its population included groups such as the Zapotecs, Mixtecs, Maya, and Otomi, who likely lived in distinct residential quarters. 

From the perspective of later Aztec visitors, Teotihuacan was already a sacred ruin and they gave it the name, which means “the place where the gods were made”.

However, the original name used by its builders is unknown. Regardless, as a centre of trade, the city controlled important sources of green obsidian at Pachuca, valued for its quality, and exported finished blades, figurines, cotton textiles, exotic bird feathers, and ornaments throughout Mesoamerica.

Its merchants likely travelled as far as Tikal in the Maya lowlands, and this spread Teotihuacan's influence to regions outside the Basin of Mexico. 

One of the most notable features of Teotihuacan was its very organised city layout.

The city stretched over 20 square kilometres and followed a grid pattern aligned about 15.5 degrees east of north.

The Avenue of the Dead, which measured about 4 kilometres in length, was the main route and connected ceremonial, residential, and administrative areas. 

At the northern end of this avenue stood the Pyramid of the Moon, which faced the Cerro Gordo mountain and dominated a large public plaza capable of holding tens of thousands of spectators.

The structure stood over 40 metres high and consisted of several building stages that ended in the massive platform visible today.

Archaeologists have found offerings of obsidian, figurines, and animal remains buried beneath its foundations. 

In the central area of the city, the Pyramid of the Sun rose more than 65 metres, which made it among the largest pyramids in the world by volume.

Workers constructed it over a natural cave that had likely held religious significance before the city expanded.

Excavations under the pyramid uncovered a series of chambers filled with ritual deposits, which included obsidian knives, shells, and carved statues arranged in symbolic patterns.

The pyramid and many other structures were once painted in vivid red, white, and ochre pigments, which would have created a striking visual impression. 

In the southern district, the Ciudadela housed the Temple of the Feathered Serpent.

It is named this because the temple’s front displayed hundreds of carved serpent heads and marine symbols, which may have connected the building to both fertility and warfare.

Beneath the temple, archaeologists uncovered the remains of approximately 260 sacrificial victims, based on current archaeological estimates.

Many were young men buried with weapons, jewellery, and ceremonial clothing.

This suggests that the structure had both religious and political purposes. 

In residential zones, apartment compounds housed hundreds of people in close quarters.

These complexes included private rooms, courtyards, storage areas, and painted walls covered in religious and decorative images.

Mural art focused on shared religious figures, such as the "Great Goddess", and cosmic symbols, which point to a standardised belief system promoted throughout the city. 

After 550 CE, Teotihuacan experienced a rapid decline. Burn layers in key buildings, such as the Temple of the Feathered Serpent and elite palaces, suggest a coordinated act of destruction.

Many researchers argue that internal revolt or class conflict may have played a role in the city's collapse. 

In addition to political turmoil, the city likely faced agricultural and environmental difficulties.

Population growth placed stress on irrigation systems and farmland, and climate data from lake sediment cores points to severe droughts in the 6th century CE that may have led to crop failures.

As resources fell and public confidence in the ruling class fell, Teotihuacan began to lose its stability. 

Trade routes also changed during this period. Several goods that once flowed into the city, such as jade and seashells, with limited or uncertain evidence for cacao, became scarce.

Regional competitors gained influence, and Teotihuacan lost its status as the central power in central Mexico.

As control weakened, many neighbourhoods were abandoned. 

Over the next few generations, the population declined sharply. The great avenues and temples no longer served administrative or ceremonial purposes.

While some families continued to live in peripheral areas, the central city became a relic of a vanished order. 

In the fourteenth century, the Aztecs encountered Teotihuacan as they expanded their influence in the Valley of Mexico.

They found a vast, empty city whose monuments stood in silence. Rather than treat it as a ruin, they regarded it as a sacred place of divine origin. 

Among the Aztecs, religious leaders made pilgrimages to the site, offered tribute, and performed ceremonies among its abandoned structures.

They did not attempt to rebuild the city but instead wove its remnants into their own worldview, and they held festivals there as part of their ritual calendar. 

Tenochtitlan, the Aztec capital, even mirrored aspects of Teotihuacan’s layout. Its twin pyramids, ceremonial plazas, and street organisation echoed what the Aztecs had seen in the ancient ruins.

As they adopted and repurposed the site’s heritage, they connected their empire to a deeper religious and cultural past. 

According to Aztec myth, the gods gathered at Teotihuacan after the destruction of the previous world.

They agreed to create a new sun, but someone had to sacrifice themselves to make the sun rise.

Two deities, Nanahuatzin and Tecciztecatl, stepped forward. Both threw themselves into the divine fire and, according to later Aztec belief, became the Sun and the Moon. 

Following this, the other gods offered their lives to ensure that the sun moved across the sky.

The story became central to Aztec ritual life. Blood sacrifice, which the Aztecs practised widely, derived its justification from this foundational myth. 

From their perspective, the Pyramid of the Sun was the exact spot where this cosmic event took place.

The Avenue of the Dead became the path taken by the gods in the sacred age before time.

When they tied their rituals to Teotihuacan, the Aztecs reinforced their religious authority and explained their place in the divine cycle. 

Over the last few decades, new discoveries have transformed the understanding of Teotihuacan.

In 2003, a tunnel beneath the Temple of the Feathered Serpent was rediscovered and, inside, archaeologists found thousands of ritual objects, which included carved stone figures, obsidian blades, rubber balls, and traces of liquid mercury, which was announced in 2015.

Some archaeologists have suggested that the mercury may have symbolised an underworld river, though this idea is uncertain. 

As mentioned above, unlike Maya or Zapotec cities, Teotihuacan avoided glorifying individuals.

Religious symbols, animal motifs, and celestial themes appeared instead.

Tombs excavated near ceremonial centres contained individuals with foreign dental inlays and cranial modification methods.

These remains show contact with distant regions and may point to the presence of envoys, merchants, or captives.

In some cases, burial goods included jade likely sourced from the Motagua Valley in Guatemala, based on geological analysis and shells from coastal areas. 

Mass graves, especially around temples, revealed evidence of human sacrifice on a large scale.

Warriors, children, and others were buried with items that showed their role in rituals.

Each group appeared to serve a different purpose in the city’s ceremonial life, from displays of military power to appeals for divine favour. 

With the help of LiDAR scanning and geophysical surveys, archaeologists continue to map parts of the city buried under farmland and modern towns, and this work has revealed more than 200 previously unknown structures.