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Do long-dead builders have the answer to more sustainable road development? A new exhibit at the Smithsonian Institution in Washington DC shows why the Incan kingdom built a lasting infrastructure.
The Inca Road is one of the most extraordinary feats of engineering in the world. By the 16th Century it had helped transform a tiny kingdom into the largest empire in the Western hemisphere.
And to the envy of modern engineers, substantial parts of the 24,000-mile (39,000-km) network survive today, linking hundreds of communities throughout Argentina, Bolivia, Chile, Colombia, Ecuador and Peru.
Incredibly, it was constructed entirely by hand, without iron or wheeled transportation.
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