By Raveen Singh

The year is 1325. According to a myth, a nomadic tribe moved into an area previously occupied by several other tribes, with the intent to settle. As such, a King of the existing tribe offers his daughter’s hand in marriage to the incoming nomads.

The Nomads, the Sacrifice, and the Lake

The nomadic tribe receives the young woman and prepares her for marriage in accordance with their customs. Then five men lead her to the top of a stone cairn, where a slab of rock awaits. They lay her down and hold her, one man per limb. The fifth man lifts a piece of obsidian over his head and plunges it into her heart, reaching in and ripping it out with his bare hands. Later that night, at a presentation for the King, they wore her glistening skin as they performed a ceremonial dance.

Once the King realized what had been done, he was clearly angered. Legend has it that he ordered the nomads to be destroyed, a chase ensued, and the nomads plunged themselves to safety in Lake Tenochtitlan. On an island in that lake, the nomads saw a vision: an eagle perched on a cactus eating a snake. This was a sign to the nomadic tribe to settle there; they called themselves the Mexica.

The Nomads Settle Down and Build

The Mexica, later called the Aztecs, were forced to adapt to their new inherited island in the middle of a large saline lake surrounded by four other freshwater lakes. To settle this area, found by chance but validated by their deity, would require feats of engineering far ahead of the times.

The lake beds comprise extremely soft soils, incapable of supporting heavy structures such as houses, roads, buildings, bridges, or most importantly, temples. The Aztecs somehow figured out how to drive piles into the muck, which contained fill to provide support for building a temple. Now known as the Templo Mayor, it was the central focal point of the new settlement.

Causeways. Initially, the only access to the area was via water and canoes. The Aztecs then required access to the mainland, so they placed fill into the soft lake beds. The fill would settle out of sight into the soft substrate, the Aztecs drove an array wood piles into the fill, and created the basis for building roads. Because all the construction materials were placed by human hands, as the Aztecs had no animals to help with the tasks, they made every effort to reduce the materials requiring transport. Eventually, using the fill-and-piling method, they constructed five causeways to link the mainland to the Templo Mayor.

The settlement, called Tenochtitlan, was centralized around the Templo Mayor, and the Aztecs realized that the obstacle that they had to surmount was also the very thing that provided them security – the lake itself.

Chinampas. As the settlement grew, they realized that their food supply required security against hostile invading tribes and the Aztecs eventually perfected the use of chinampas (floating gardens) as a means of ensuring a stable large-scale cultivated food supply. The chinampas were made of interwoven reeds with stakes beneath the surface of the water, creating underwater fences. Atop these mats, they added lake sediment mixed with aquatic vegetation until the top layer was above the surface. This type of construction would ensure that the crops would always have a water supply, requiring minimal maintenance.

Drainage, Dikes, and Canals. The Mexica also developed a multipurpose drainage system, which comprised a ditch for the flow of water and sediment (which likely included human waste) that would in turn be used in the development of new chinampas. Because of the biological diversity of the introduced sediment and the use of lake-bed sediments, the bacterial community was diverse, thus supporting virtually every type of crop. With these raised, well-watered beds, the crop yields were very high, permitting up to seven harvests per year. In 2018, the United Nations designated the chinampa system of agriculture a Globally Important Heritage System; it should be noted that it is still in use today.

Construction in a low-lying land such as a lake bed also required advanced techniques to control flooding. An area with impermeable soils and no drainage required a method of ensuring that water levels in the area of habitation were maintained. Dikes, canals and causeways were built as a means of flood control, including a 16-km long dike that held back a portion of Lake Texcoco to prevent seasonal flooding. The Aztecs also built a series of canals through the city to drain the swamplands, and earthen causeways that also served as pedestrian walkways. A series of locks, gates, and sluiceways were built into the system a means of controlling water levels, an engineering feat far ahead of its time.

Aqueducts. Water, the sustenance of life, was also initially a challenge to the Aztec. The waters of the lake at the location were saline and not sustainable for long-term use for humans. The Aztecs found a series of springs on the mainland, and developed an aqueduct to transmit this water to the island city. Initially, water was brought in by canoe, which would have sharply limited the growth of the society.

An Expanding Empire. The aqueduct required negotiations with the adjacent tribe, who required that the Aztecs cede themselves to rule by the mainland tribe. As the Aztec society grew due to prosperous food supply and engineering, they conquered the governing tribe; the governed became the government. It is at this time that the Aztecs underwent a rapid expansion, conquering other tribes such as the Olmecs and Toltecs, and taking their people as workers, slaves, and sacrificial victims. These conquests allowed the Aztecs to preserve their society and expand their empire as far away as Guatemala and from the Gulf of Mexico to the Pacific Ocean.

Other systems developed by the Aztecs long before being colonized include the military draft (conscription), and a legal system with judges and trials. Using the cocoa bean as currency, their busiest days in the markets of Tenochtitlan drew some 50,000 people.

The Demise of the Aztecs

In 1521, Hernán Cortés arrived on the Yucatán peninsula and found his way to Veracruz. The indigenous population joined him on his march to the head state of the Aztec Empire. The Spanish were in awe of the progress that the Aztec society had made, which paralleled some of the advanced systems in Europe at the time. The floating gardens and the prominence of the Templo Mayor must have been a sight to the Spanish conquistadors.

Of course, the story of the Spanish and their rapid conquest is full of sadness; the destruction of Aztec society by the Spanish was accomplished through the introduction of disease, advanced weaponry comprising steel, and the use of horses for the height and mobility advantages. Those who are interested are encouraged to read Guns, Germs, and Steel: The Fates of Human Societies, by Jared Diamond (1999), for a better accounting of how colonizing European armies could so easily conquer the societies they met through exploration.

In a final death blow to the Aztecs empire, all the structures of Tenochtitlan were destroyed and the building materials were dumped into the lake to form the foundation for the new Spanish settlement, called Mexico. The causeways were converted into roadways (still in use today); the aqueducts were destroyed. The Templo Mayor was razed to the ground, and in an act of conquest, the new Spanish cathedral was built atop the old Templo Mayor. This was only discovered in 1978, as a dig for a utility in the area encountered remnants of the old structure. Today, the area is preserved as a tourist attraction in the zócalo in Mexico City, where it is possible to pass under the church and view the Templo Mayor. In less than 200 years, the advancement of the society of the Aztecs can only be described as profound and its demise as tragic.

Montezuma’s Revenge

There are many tales in folklore regarding Montezuma’s revenge; however, this is an obscure one that the old civilization has left behind.

Like many modern cities that are built on marine environments (think Jakarta, Venice, Amsterdam, New Orleans, Bangkok, Kolkata, Tokyo, and even Washington DC), Mexico City underwent an astounding period of growth in the early 20th century, building on its legacy as a capital founded by the Aztecs.

However, the construction on the lake bed has had a lasting impact on modern day Mexico City. The increased weight of the colonial settlement over time has resulted in compression of the soils, and the pumping of water from the subsurface has drawn down the water table. This in turn has reduced pore pressures in the underlying soils, thus increasing the rates of settlement.

It is said that there are places in Mexico City that are settling up to 500 cm per year. This has resulted in buckling of roads, bursting of utilities, and damaged buildings as walls topple and fail. Compounded with earthquakes, the destruction is multiplied; in 1985 the earthquake that struck Mexico City caused widespread devastation, associated in part with soil-structure interaction and poor building foundations. As of the writing of this article, there is no known solution to this long-term problem. The lake, or its remnants, continue to be dewatered as development continues, exacerbating the condition. It is said that in the last century, Mexico City has subsided some 33 feet.

Perhaps Montezuma’s revenge is more profound than modern society ever thought it could be.