Engineering Marvels of the Inca Empire

Arts and Media May 2024 PREMIUM

The Inca Empire’s remarkable architectural achievements and sophisticated infrastructure are a testament to ancient civilizations’ ingenuity and technological prowess. From their intricate road networks to their innovative irrigation systems and agricultural methods, the Incas developed a range of technologies that enabled them to thrive in the challenging Andean environment. 

The Inca Road System

Among their many achievements, The Inca Road system, known as the Inca Road or Qhapaq Ñan, stands out as it spanned nearly 40,000 kilometers (25,000 thousand miles) across their empire. Many of these roads, wide and paved with stone, were engineered to make level routes in mountainous regions. Inca runners, known as chasquis, part of this sophisticated communication system, relayed messages across the empire at remarkable speed. When roadways were impossible, they built, for instance, suspension bridges of braided cables made of grass and reeds. These bridges could span as high as 45 meters (150 feet). Other bridges were built of stones or floating reeds. This intricate road system enabled centralized governance and facilitated communication, trade, and the movement of troops and food supplies to Cusco or those communities whose crops had produced poorly.

Stone Masonry and Construction Techniques

Their impressive stone masonry and construction techniques allowed them to create durable structures from temples and fortresses, such as Machu Picchu and Sacsayhuamán, and agricultural terraces to smaller structures, like colcas and tampu, which continue to inspire awe and admiration centuries after their construction. The colcas, were storehouses built of flagstones and thatch roofs, aligned in rows using an engineering and location that allowed them to keep the contents dry and cool. They used them to store all kinds of goods, from food to clothing and weapons. The tampu, built with fieldstone in the mountains and adobe (a mixture of mud and straw) on the coast, served as temporary housing for royals, soldiers, and workers. 

One technique, called Ashla Masonry, consisted of cutting and shaping individual stones and making them fit together in seamless joints with astonishing precision and without using mortar. The joints are so tight that fitting a blade between them is impossible. They also used cyclopean masonry to fit large stones of irregular shapes in order to build walls and buildings. The fortress of Sacsayhuamán, located near the Inca capital of Cusco, was built in the 15th century. If Cusco was laid out as a puma, then Sacsayhuamán represents the puma’s head. Here, massive stone blocks up to 8 meters (27 feet) high, weighing many tons, were precisely cut and fitted together to form enormous zigzag walls, becoming a feat of human engineering. The precision of the construction is such that even today, experts marvel at how the stones were shaped and positioned with such accuracy. 

Agricultural Technology

The Incas were pioneers in agricultural technology, developing innovative techniques such as terracing, irrigation systems, and crop rotation. These advancements allowed them to cultivate crops at high altitudes, overcoming the numerous challenges presented by the Andes, such as rugged terrains, sharp slopes, thin soil, and unpredictable weather. One of their most remarkable agricultural innovations was the use of terracing. They carved stepped platforms into the hillsides, progressively steeper from the valleys up the slopes, effectively expanding the amount of arable land available to them. These flat surfaces also helped prevent soil erosion and retain moisture, allowing crops to thrive in the harsh Andean environment. Today, locals are rebuilding terraces and irrigation systems inspired by recent archaeological research, as Incan agricultural techniques seem to be more productive and more efficient, particularly in terms of water use. These modern farmers also believe the Incan techniques can offer simple solutions to protect communities’ food supply facing climate change.

Water Management System

Last but not least is the Incas’ water management system. Through a network of canals, aqueducts, and reservoirs, the Incas could ensure water supply with a consistent water-carriage system even in areas with limited rainfall while ensuring water disposal during heavy rain. Such is the case of Machu Picchu. It was built in roughly 90 years in the 15th century. The Incas may have planned it for a year or two. In a first stage, they studied the underground, did foundations and site preparation and planned some 130 drainage holes during the initial construction of the walls. In an excavation done in the Plaza, it was found that under a 3 feet rich topsoil, there is a sandy, gravelly-type soil, and below that, a subsurface drainage system made out of waste rock from all of the stones that they’d been cutting for years and years before. Without that good drainage, there would be no Machu Picchu today, as there are about 76 inches of rain per year, mainly during the wettest seven months or so. The terraces have a high permeability, allowing the water to go underground and be carried away. The mountain would have slid without terraces, so they fulfill the double function of stabilization and support and provide a more extended agricultural area. 

Machu Picchu’s layout is basically controlled by the Inca spring. As the spring’s location was fixed, the Inca engineers figured out the slope of the canal and set it at an average of about 3% and a length of about 2,500 feet. There are 16 fountains, which handle about 25 gallons per minute. If run-off water came into the canal during heavy rainfall, the Inca engineers installed two safety valves, one in the middle of the agricultural zone, which would discharge onto the agricultural slope and infiltrate into the ground, and another at the main drain. So, there is a balanced system all the way from the spring to the main drain.

The Incas were concerned with maintaining pure water, as the water supply canal was built in such a way that it would be well isolated from drainage holes and potential pollution. As the Emperor was to be the first in the use of water, his residence was built near Fountain One. Also, his was the only house with a sanitary drain, and it didn’t go to any place where it could possibly contaminate. Thus, they had a sense of hygiene and pure water long before Westerners did.

The technological achievements of the Inca Empire are a testament to the ingenuity and resourcefulness of this ancient civilization that built for the ages. By understanding and appreciating these achievements, we gain insight into the remarkable accomplishments of one of history’s greatest civilizations.


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