By tradition the Mexica founded Tenochtitlan in 1325 CE on a marshy island in Lake Texcoco, where, prophecy held, they saw an eagle perched on a cactus. From this constrained lacustrine site they built a planned capital of canals, causeways and chinampas around a walled ceremonial precinct, the whole laid out on a quadripartite division aligned to the cardinal directions. Within two centuries it grew into one of the largest cities on Earth, holding perhaps 200,000 people. Its plan reconciled cosmological order with the engineering demands of building a metropolis on water.
It is the archetypal pre-Columbian planned metropolis and the direct substrate of Mexico City, the largest city in the Americas. Its founding shows deliberate, cosmologically ordered city-making on one of the most difficult sites ever urbanised.