According to Aztec tradition, wandering Mexica people saw an eagle devouring a serpent atop a cactus on a swampy island in Lake Texcoco, fulfilling a prophecy that marked where they should build their city. Tenochtitlan grew into the magnificent capital of the Aztec Empire, later conquered by Spanish forces, its ruins now underlying modern Mexico City.
The story is one of the most enduring founding myths in the Americas: the Mexica people, having wandered for generations searching for a sign from their god Huitzilopochtli, finally saw it on a small island in the marshy expanse of Lake Texcoco—an eagle perched on a prickly pear cactus, a snake writhing in its talons. This was the promised place, and there they began to build.
What rose from that swampy island over the following two centuries defied its humble origins entirely. Tenochtitlan became one of the largest cities on Earth, a marvel of causeways, canals, floating gardens called chinampas, and towering temple pyramids, home to as many as 200,000 people by the time Spanish conquistadors arrived in 1519.
Hernán Cortés and his men were reportedly stunned by its scale and order, comparing it favorably to European capitals. The empire's fall came swiftly and brutally through conquest, disease, and siege, but the symbol endured: the eagle on the cactus devouring the serpent sits today at the center of the Mexican flag, a nation's identity rooted in a vision from a wandering people seven centuries ago.