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The Urban History of the Valley of Mexico
By Caitlin Chan
The Valley of Mexico, home to Mexico City, is situated within a ring of high-altitude mountains in central Mexico. This was historically a landscape characterized by its shallow, wide-ranging lake system, surrounded by marshes, including the Lakes Zumpango, Xaltocan, Xochimilco, Chalco, and the largest, Texcoco. However, after the arrival of Spanish conquerors in the sixteenth century, the lakes in the Valley of Mexico, primarily Lake Texcoco, were drained over several centuries, leading to widespread environmental effects. Spanish colonial authorities viewed water as an obstacle rather than as an asset, replacing Aztec water management with massive canal and tunnel projects, transforming the wetland basin into a largely dry, paved-over urban landscape. The history of urbanization and colonization in this region is a story fundamentally tied to water.
The basin has a base elevation of around 7000 feet (2,133 m) above sea level, and the valley floor itself reaches 8000 feet (2,438 m). The surrounding mountains extend even further into the sky, peaking at 16,000 feet (4,877 m) above sea level. The valley was first settled by an unknown group of farmers in 200 B.C.E., who built small villages and tilled fields near the saline shores of Lake Texcoco. It was not until 100 C.E. that the region began to develop as a center for population and industry.
Teotihuacan was built around 100 C.E. by an ancient Mesoamerican society, whose identity remains unknown. In fact, archaeologists today do not actually know the true name of Teotihuacan—it was long abandoned by the time that the Aztecs reached the site and dubbed it “Teotihuacan,” Nahuatl for “the city of gods.” It was both a religious and urban center—at its peak in 650 C.E., the city was one of the largest preindustrial settlements in the world, with a population somewhere between 25,000 and 80,000. This population was highly multiethnic, with people from all of the areas surrounding the Valley of Mexico. However, much of the city was reserved for the elites while the rest of Teotihuacan’s inhabitants lived and farmed on its outskirts.
As an urban space, the city was divided into four quadrants by two large avenues with a gridded layout, interspersed by an irrigation system of spring water. This organization was informed by the valley’s landscape and the builders’ cosmology. When constructing the Avenue of the Dead, which crosses the city from north to south in its ceremonial center, engineers altered the course of the San Juan River to fit the urban layout and intersect with the avenue. Along the avenue lie the terraced pyramids for which Teotihuacan is most famous: the Pyramids of the Sun and Moon and the Temple of Quetzalcoatl, the serpent god. However, the city succumbed to a fire in the seventh century and was subsequently abandoned, long before the Aztecs arrived in the area. In this intermediary period, a variety of groups invaded the valley, though none stayed long enough to establish a Teotihuacan-level presence in the region. For the most part, the remaining inhabitants fell under the rule of the Toltecs or Chichimec tribes throughout the following centuries.
Around 1200 C.E., the Aztecs swept down from north-central Mexico into the sparsely populated valley. By 1353, they had established the town of Tenochtitlan on an island in Lake Texcoco and quickly took control of the rest of the lake-dwelling peoples. After another century, Tenochtitlan became the bustling urban capital of the wide-ranging Aztec empire. It was vast, with a carefully planned street system, gardens, monuments, and bridges spanning the lake. When the Spanish arrived in the city in the sixteenth century, it contained over 400,000 inhabitants—the largest of any Mesoamerican settlement in history. As in Teotihuacan, the city contained a sacred center where Aztecs worshipped their vast pantheon of deities and celebrated their cosmological devotion to the sun. Additionally, in Tenochtitlan and throughout the rest of the empire, Nahuatl was designated the official language of the Aztecs and was written in icons and symbols prevalent throughout the city.
The triumph of the builders of Tenochtitlan was their innovative systems of urban, architectural, and agricultural planning atop the shallow lake, as they expanded the island to cover over 5 square miles (13 square kilometers) through the use of chinampas, a system of farming by creating small artificial islands. Farmers constructed these islands by filling up rectangular sections of the lake with lakebed mud and brush in layers, slowly raising them to the surface to become fertile new landforms. They were navigable by the small willow-lined canals that spread through the island grid. With the development of the chinampa system, the city was fed year-round and could accommodate far more residents than the original Texcoco islands. These chinampas are still present and in use today, particularly at the fringes of Mexico City.
Tenochtitlan was also notable for its sanitation, as human waste would be constantly swept into the lake. Because the lakes of the Valley of Mexico were landlocked, they had no natural outlet. The Aztecs devised ways to recycle the nutrients from this waste to improve agricultural outputs without destroying the lakes’ ecosystems. To provide drinking water, then, the Chapultepec aqueduct was built in 1418 to channel freshwater into the city (though the mud and tree trunks used for its construction were not always reliable). It was reinforced after it failed in 1449, and a brand-new channel was built during the Spanish colonial period.
In 1519, the golden age of the Aztecs ended with the arrival of Spaniard Hernán Cortés and a band of conquistadors hoping to expand the realm of the Spanish empire. After two years of battling with the Aztecs, the Spanish laid siege to Tenochtitlan—then led by Emperor Montezuma II—and took control of the city in 1521. Tenochtitlan’s residents were weakened by a smallpox epidemic brought by European viruses and by the superior weaponry of the conquistadors, and soon had to surrender after their fierce defense of their city. The Spanish subsequently razed and looted Tenochtitlan, leaving behind a crumbling city over which Cortés could take control. He founded Mexico City and began the construction of a new capital over the ruins of the old.
The incoming Spanish residents of Mexico City became frustrated with managing life on the lake, as the city flooded frequently, hindering urban development. Over the next few centuries, engineers systematically drained the lakes (beginning with Lake Texcoco), a process that destroyed the valley’s aquatic ecosystems and led to widespread environmental degradation. Rather than adapting to nature as did the Aztecs and previous residents of the valley, the effects of the Spaniards’ massive hydraulic engineering project to drain the Valley of Mexico’s ancient lakes are a testament to the disastrous effects of attempting to control nature and its resources. Today, environmental engineers are developing ways to revitalize the lakes in Mexico City to combat pollution. Once one of the largest ancient cities in the world, with around 400,000 residents, Mexico City retains this distinction as the largest city in the Western Hemisphere, with over 22 million people in its metropolitan area. Also, it remains one of the most biologically diverse regions in Mexico, and it is instructive to look to the Aztecs as an example of how to develop environmentally conscious urban landscapes.
References
Allen, L. (2025, October 13). Lessons from the chinampas: How the Aztecs recycled human nutrients for a clean, green city | Ocean Sewage Alliance. Ocean Sewage Alliance. https://www.oceansewagealliance.org/newsroom/lessons-from-the-chinampas-how-aztecs-recycled-human-nutrients-for-a-clean-green-city
Chinampas in Mexico is an indigenous and highly sustainable agriculture system. (2021, August 9). PreventionWeb. https://www.preventionweb.net/news/chinampas-mexico-indigenous-and-highly-sustainable-agriculture-system
Evans, S. T. (2007). Precious Beauty: The Aesthetic and Economic Value of Aztec Gardens. In M. Conan (Ed.), Botanical Progress, Horticultural Innovations, and Cultural Changes. Dumbarton Oaks.
Mason, J. A. (1943). The Valley of Mexico: American Collections. The Ancient Civilizations of Middle America. Penn Museum Bulletin, X(1–2).
Pre-Hispanic City of Teotihuacan. (n.d.). UNESCO World Heritage Centre. Retrieved April 22, 2026, from https://whc.unesco.org/en/list/414/
Pública, A. D. de I. (n.d.). Chapultepec Fountain & Aqueduct. Mexico City. Retrieved April 22, 2026, from https://mexicocity.cdmx.gob.mx/venues/chapultepec-fountain-aqueduct/
Rose, S. (2019, March 16). Aztec Architecture: Floating Gardens & Aqueducts in Tenochtitlan. Blurred Bylines.https://blurredbylines.com/blog/tenochtitlan-aztec-architecture-agriculture/
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