New detection technologies have helped a team of American and Uzbekistani researchers map a pair of cities that were once part of the ancient Silk Road trade route across Asia.

Aerial light detection and ranging, also known as lidar, helped the researchers develop a plan of the fortifications and urban architecture at the sites of Tashbulak and Tugunbulak, the latter of which spanned more than 296 acres, according to the abstract of their study, published in the journal Nature.

Tashbulak was about one-tenth the size of Tugunbulak, and both, at about 6,600 feet above sea level, sit about as high in their mountains as Machu Picchu does in the Andes. The sites are thought to have been occupied in the sixth to 11th centuries, a time coinciding with the expansion of the Turkic people and the arrival of Islam in the region.

“While typically seen as barriers to Silk Road trade and movement, the mountains actually were host to major centers for interaction. Animals, ores and other precious resources likely drove their prosperity,” said Michael Frachetti, a professor of archaeology at Washington University in St. Louis.

While the sites were found between 2011 and 2015, the use of the latest lidar sensors on 17 drone flights meant work that could have taken a decade was completed in just three weeks, Mr. Frachetti said in a statement from the school.

Early digging at Tugunbulak suggests the city could have sprung up around ore deposits as a regional blacksmithing center. Pottery, coins and jewelry that could have been exchanged for other goods have also been found at the sites, Uzbekistan National Center of Archaeology Director Farhod Maksudov told The New York Times.

Iron was key to the production and trade of weapons. 

“Whoever had iron in their hands in medieval times was very powerful,” Mr. Maksudov told the BBC. But cutting the forests to fuel the forges led to environmental instability, including floods and avalanches.