Over the centuries, the empire’s grass bridges gradually gave way, and were replaced with more conventional works of modern engineering. The most famous Incan bridge—the 148-footer immortalized by Thornton Wilder in The Bridge of San Luis Rey—lasted until the 19th century, but it too eventually collapsed. Today, there is just one Incan grass bridge left, the keshwa chaca, a sagging 90-foot span that stretches between two sides of a steep gorge, near Huinchiri, Peru. According to locals, it has been there for at least 500 years.
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