The Inca road system (also spelled Inka road system and in Quechua: Qhapaq Ñan meaning "royal road") was the most extensive and advanced transportation system in pre-Columbian South America. It was about 40,000 kilometres (25,000 mi) long in total. The construction of the roads required a large expenditure of time and effort. The network was composed of formal roads carefully planned, engineered, built, marked and maintained; paved where necessary, with stairways to gain elevation, bridges and accessory constructions such as retaining walls, and water drainage systems.
An empire connected by routes
I believe that, since the memory of people, it has not been read of such a greatness as this road, made through deep valleys and high peaks, snow covered mountains, marshes of water, live rock and beside furious rivers; in some parts it was flat and paved, on the slopes well made, by the mountains cleared, by the rocks excavated, by the rivers with walls, in the snows with steps and resting places; everywhere it was clean, swept, clear of debris, full of dwellings, warehouses for valuable goods, temples of the Sun, relay stations that were on this road.
The Tawantinsuyu, which integrated the current territories of Peru, continued towards the north through present-day Ecuador, reaching the northernmost limits of the Andean mountain range in the region of Los Pastos in Colombia; by the South, it penetrated down to the Mendoza and Atacama lands, in the southernmost reaches of the Empire, corresponding currently with Argentine and Chilean territories. During the Inca Empire, the roads officially stemmed from Cusco into the 4 cardinal directions towards the 4 suyus (provinces) into which the Tawantinsuyu was divided. Cusco was the center of Peru: the Inca-Spanish chronicler Inca Garcilaso de la Vega states that "Cozco in the language of the Incas means navel that is the Earth's navel". The four regions were named Chinchaysuyu towards the North, Collasuysu towards the South, Antisuyu towards the East and the lower valleys of the Amazon region and Contisuyu towards the West and the lower valleys along the Pacific coast.
Messages, armies, and travel
Transportation was done on foot as in pre-Columbian America; the use of wheels for transportation was not known. The Inca had two main uses of transportation on the roads: the chasqui (runners) for relaying information (through the quipus) and lightweight valuables throughout the empire, and llamas caravans for transporting goods. Llamas were used as pack animals in large flocks. They are lightweight animals and cannot carry much but are incredibly nimble.
To transport large numbers of goods across the empire, it was more efficient for the Incas to use herds of llamas and to have two or three herdsmen. These roads provided easy, reliable and quick routes for the Empire's administrative and military communications, personnel movement, and logistical support. After conquering a territory or convincing the local lord to become an ally, the Inca would employ a military-political strategy including the extension of the road system into the new dominated territories.
The Qhapaq Ñan thus became a permanent symbol of the ideological presence of the Inca dominion in the newly conquered place. The road system facilitated the movement of imperial troops and preparations for new conquests as well as the quelling of uprisings and rebellions. Roads and bridges were essential to the political cohesion of the Inca state and to the redistribution of goods within it. All resources in the Empire were the property of the ruling elite.
Building across difficult terrain
The manpower required for both construction and maintenance was obtained through the mita: a sort of tax work, provided to the state by the conquered people, by which the Inca Empire produced the required goods and performed the necessary services, which included the upkeep of roads and their relevant infrastructures (bridges, tambos, warehouses, etc.). The labor was organized by officials who were in charge of the development, control and operation of roads and bridges, as well as communications. In the mountains and the high forests, precisely arranged paving stones or cobbles were used for paving, placing them with their flat face towards the top, trying to produce a uniform surface.
Nevertheless, not all the roads were paved; in the Andean puna and in the coastal deserts the road was usually made using packed earth, sand, or simply covering grassland with soil or sand. Drainage by ditches or culverts was more frequent in the mountains and jungle due to the constant rainfall. Along other road sections, the drainage of rain water was carried out through an articulated system based on longitudinal channels and shorter drains, transverse to the axis of the road. Retaining walls were used along the mountain slopes, and are similar to those used to support the terraces. There were multiple types of bridges used throughout the road system and they were sometimes built in pairs.