How the Inca Leapt Canyons

A fascinating story from John Noble Wilford, for the New York Times.  
Yet the suspension bridges were familiar and vital links in the vast empire of the Inca, as they had been to Andean cultures for hundreds of years before the arrival of the Spanish in 1532. The people had not developed the stone arch or wheeled vehicles, but they were accomplished in the use of natural fibers for textiles, boats, sling weapons — even keeping inventories by a prewriting system of knots.
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