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

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.
Part of the bridge's strength and reliability came from the fact that each cable was replaced every year by local villagers as part of their mit'a public service or obligation. In some instances, these local peasants had the sole task of maintaining and repairing these bridges so that the Inca highways or road systems could continue to function.