An exhibition at the National Museum of the American Indian is the result of six years of research that concludes the ancient Incas knew a thing or two about water.
"When you look at Machu Picchu in Peru - that wonderful structure on top of the mountain that millions of tourists visit every year - what most people don't see and unfortunately don't know, is that the real marvel is underneath it all," says Jose Barreiro, co-curator of The Great Inka Road (the Smithsonian uses the Quechua spelling of Inca).
The dry stone monument sits on top of a complex irrigation system of culverts and channels that control the flow of water into fountains that still work today. And while archaeologists have known that for some time, the exhibition reveals the extent of the Inca understanding of water and how they applied the same technology to road building.
"Every year, water destroys many modern roads. But the Inca roads tend to stay," says Barreiro.