“Khipu” were Incan devices that used string knotted in various ways to record information such as census reports and historical events. This one is dated between A.D. 1400 and 1600. (Ernest Amoroso/National Museum of the American Indian)

Infrastructure was critical to the success of South America’s greatest empires. Built without the use of metal, wheels or draft animals in the 15th century, an immense system of roads united more than 100 native cultures and millions of people in the Tawantinsuyu confederation over a challenging terrain along the northern and central coast of the continent.

Some segments of this ancient engineering feat still survive and are honored as a sacred space. It’s being celebrated in a major exhibition that opened last week at the Smithsonian’s National Museum of the American Indian.

“The Great Inka Road: Engineering an Empire” shows that parts of the road — including some rope bridges across mountain valleys — are still being rebuilt, in certain cases annually, in the manner of their ancestors. (The exhibition title uses a less common spelling of “Inca,” consistent with the traditional South American language of Quechua and the museum’s policy on native languages.)

It was one of those achievements where
numbers really do tell the story.


Estimated length, in miles, of the road system, which fed off two main roads north to south, one along the coast and the other through the Andean highlands.

An Incan bag embellished with images of llamas, circa A.D. 1450-1532. (Ernest Amososo/National Museum of the American Indian)

Modern-day countries traversed from north to south by the roads: Colombia, Ecuador, Peru, Bolivia, Argentina and Chile.


Approximate number of years the road system was in use until the Spanish invasion of 1532.


Number of earlier cultures whose routes were adapted by the Incas: Wari, Tiwanaku and Chimu.


Height, in feet, of the highest mountain pass on the 20-mile spur to Machu Picchu.


Length, in meters, of the most famous rope suspension bridge, made using braids of reed or grass. It crosses the Apurimac River near Cusco.


Objects in the show, including gold ornaments, shell necklaces, silver and gold figurines, stone carvings and textiles.

800-100 B.C.

Estimated age of oldest artifact on display: a ceramic stirrup-spout bottle from the Chavin culture.


Regions that made up the empire: Chinchaysuyu, Antisuyu, Collasuyu and Contisuyu, with the capital of the regions, Cusco, in the center of what is now Peru.


Number of years indigenous people have been continuously remaking a suspension bridge north of Cusco.


Length, in feet, of a rope suspension bridge to be built on the National Mall for the current Smithsonian Folk Life Festival.


Days left in the Smithsonian Folklife Festival Marketplace in the museum’s Potomac Atrium, closing July 12.


Years that curators Ramiro Matos and Jose Bareiro spent researching the exhibition.


Months the exhibition will be open at the museum.

Catlin is a freelance writer.

The Great Inka Road: Engineering an Empire Through June 1, 2018, at the National Museum of the American Indian, Fourth Street and Independence Avenue SW. 202-633-1000. nmai.si.edu.