Cusco Inca Rope Bridge, Apurimac Canyon, Cuzco Province, Peru

Inca rope bridges were simple suspension bridges over canyons and gorges and rivers (pongos) to provide access for the Inca Empire. Bridges of this type were useful since the Inca people did not use wheeled transport—traffic was limited to pedestrians and livestock. The bridges were an integral part on the Inca road system and are an example of Inca innovation in engineering. They were frequently used by Chasqui runners delivering messages throughout the Inca Empire.
Construction and maintenance
The Incas used natural fibers found within the local vegetation to build bridges. These fibers were woven together creating a strong enough rope and were reinforced with wood creating a cable floor. Each side was then attached to a pair of stone anchors on each side of the canyon with massive cables of woven grass linking these two pylons together. Adding to this construction, two additional cables acted as guardrails. The cables which supported the foot-path were reinforced with plaited branches. This multi-structure system made these bridges strong enough to even carry the Spaniards while riding horses after they arrived. The design naturally sags in the middle.