The Valley of Mexico is a plateau in Central America that gives Mexico its name. The Aztecs and Toltecs built their cities here and it was the epicentre of pre-Colombian civilisation. The Valley a high and fertile land, surrounded by mountains and volcanoes on four sides. Today is is home to Mexico City, the second largest in the Americas.
Mountains enclose the Valley of Mexico, with only a small pass in the north, where wind can enter. The pass was the historical migration route. As waters could not escape, the Valley once housed great lakes, the most famous of which was ‘Lake Texcoco’. Its elevation gave the Valley a cool temperature while volcanic ash made fertile soil and provided abundant obsidian – a valuable commodity.
Humans settled in the Valley of Mexico in ancient times. Beans, squash, maize and legumes grew easily here, attracting human settlement. By 1,000 AD the Valley of Mexico was one of the most densely populated areas in the world. The great city of Teotihuacan, and the Toltec civilisation that followed, were centred here.
In the 1300s, the Mexica or ‘Aztecs’ migrated from the north. Looking for a place where an eagle perched on a cactus eating a snake, they settled in the marshes of lake Texcoco. The Aztecs adopted the sophisticated culture of their neighbours and expanded across the lake, where they built the city ‘Tenochtitlan’ on an expanse of artificial islands. The city followed a plan and included marketplaces, pyramids, a palace, aquarium, zoo and botanical gardens. By the 1400s, the Aztecs were the preeminent power in the Valley, ruling their neighbours through a system of tribute and military subjugation.
In 1521, conquistador Hernán Cortés destroyed the Aztec Empire with an alliance of Spanish and native forces. He forced Aztec captives to level Tenochtitlan and built a new settlement – named Mexico City – on its rubble.
Lake Texcoco was buried. Under the weight of the ruins of the old and the streets of the new, the lake dried up. Today no trace remains. It took until 1900 for Mexico City to surpass the one million people who had lived in Tenochtitlan at its peak. By 2000, the population was 21 million.
Pollution is now rife in the Valley of Mexico. As smog and heat from cars and electricity have nowhere to escape they sit stagnant until the yearly rains. Furthermore, without the old lake to soak up the rainfall, Mexico City – particularly its shantytowns – are also prone to terrible flooding, often breaking into water supplies and creating open sewers in parts of the city. The conditions which brought cities to the Valley of Mexico, are now their greatest impediment.
Sources: Fall of Civilizations Podcast, World Health Organisation