It is an engineering marvel of antiquity, comparable, experts say, to the Roman road system, but more remarkable for the rugged terrain it has traversed for more than 3,000 years.

The Qhapaq Ñan, or “great road,” has long connected the peoples of Peru, Colombia, Ecuador, Argentina, Bolivia and Chile as it winds for thousands of miles down the Pacific Coast of South America, through snow-capped Andean peaks, tropical rain forests and desert.

Linking Cuzco, the Incan capital in present-day Peru, to the furthest outposts of the Incan empire, it carried traders, soldiers and runners, and later the horses of the conquistadors. Now, in a 12-year cooperative effort that is its own delicate feat of engineering, the six long-squabbling countries that are home to the Incan road have banded together to ask the United Nations Educational, Scientific and Cultural Organization to designate the network a World Heritage site this week. The road is one of 12 natural and cultural attractions recommended for recognition by the Unesco World Heritage Committee, which is meeting in Doha, Qatar. The application is by far the most elaborate on the list, and drew from reports by hundreds of experts who studied particular snippets of the road network or associated monuments in the various countries.

“It’s the most expansive piece of infrastructure relating to transportation in the New World,” said Gary Urton, professor of pre-Columbian studies and chairman of the anthropology department at Harvard University.