page_title: Inca road system
section_title: Bridges
hierarchical_section_title: Inca road system / Architecture and engineering of the Inka roads / Bridges
caption_attribution_description: English: Museo de Arte de LIma "MALI" - "oroya" or basket to cross rivers hanging from a rope. anonimous - Watercolor on paper - circa 1827- 1841
context_page_description: The Inca road system was the most extensive and advanced transportation system in pre-Columbian South America. It was at least 40,000 kilometres long. 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 system. It was based on two north-south roads: one along the coast and the second and most important inland and up the mountains, both with numerous branches.
  It can be directly compared with the road network built during the Roman Empire, although the Inka road system was built one thousand years later.
  The road system allowed for the transfer of information, goods, soldiers and persons, without the use of wheels, within the Tawantinsuyu or Inka Empire throughout a territory with an extension was almost 2,000,000 km² and inhabited by about 12 million people.
context_section_description: There were multiple types of bridges used throughout the road system and they were sometimes built in pairs. Some bridges were made of parallel logs tied together with ropes and covered with earth and vegetal fibers supported by stone abutments, while others were built of stone slabs resting on piled stones. One of the difficulties of creating wooden bridges was obtaining logs. Sometimes, the laborers who were making the bridges had to bring the lumber from very far away. Wooden bridges would be replaced about every eight years.
  The construction of bridges was accomplished by the help of many workers. It implied first of all the constructions of abutments, normally made of stone both rough and dressed. The masonry could even be extremely well fitted, with no evidence of any mortar being used to keep the stones in place. Inkas, having no iron, used a method of stone working which used simple tools, such as hammerstones, to pound the rocks in a way that the contours of the upper rock matched those of the rock below so that the seams fit perfectly without mortar.
  For simple log bridges, the construction was done by placing a series of logs over projecting canes. 
  Stone bridges could span shorter lengths and needed shallower rivers to be built . Some slabs were placed over the abutments and intermediate stone pillars when necessary. A very special stone bridge was recently discovered in Bolivia consisting of a relatively small opening to allow the stream to flow and a quite imposing stone embankment filling the valley sides in order to allow the road to pass on top of it.
  To cross rivers flat banks, floating reeds tied together were used, forming of a row of totora boats placed side to side and covered with a board of totora and earth.
  Inca rope bridges also provided access across narrow valleys. A bridge across the Apurímac River, west of Cusco, spanned a distance of 45 metres (148 ft). Rope bridges had to be replaced about every two years: to this end, the communities around the river crossing were commanded into a mita for the construction of the new bridge, while the old bridge was cut and let fall into the river. This type of bridge was built with ropes of vegetable fibers, such as ichu (Stipa ichu) a fiber typical of the Altiplano, which were tied together to form cords and ropes which constituted the bridge floor cables, the two handrails and the necessary connections between them.
  Ravines were sometimes crossed by hanging baskets, or oroyas, which could span distances of over 50 metres (160 ft).
caption: An "oroya" or basket to cross rivers. watercolor on paper portrayed in the Lima "MALI" museum, Anonymous - public domain
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