Two lost medieval Silk Road cities mapped in Central Asia

In a mountain-top marketplace in Uzbekistan, a trader sells Chinese silks, pots of gunpowder and jade dragon amulets, teeth-bared and grinning. Imams and Buddhist monks saunter past. The air is filled with the fine fragrance of teas, peppers and nutmeg, while breezes waft away acrid black smoke from smithies smelting steel.

A thousand years ago, inhabitants of two mountain-top cities in modern-day Uzbekistan experienced these and other impressions in their daily lives

A new study published October 23 in the journal Nature has revealed that the two cities — Tugunbulak and Tashbulak — were major urban centers that lay on medieval Silk Road trading routes.

Drone-borne scanning equipment captured images of unexpectedly large settlements ringed with watchtowers, fortresses, plazas, and homes for tens of thousands of people. 

The researchers suggest that cities located high up in the mountains may have been more important in the exchange of goods and knowledge along the medieval trade routes between East and West than previously thought.  

Two medieval cities: Tugunbulak and Tashbulak

US and Uzbekistan-based researchers used drone-based LiDAR — Light Detection and Ranging — to map the archeological sites of the two recently discovered sites in Uzbekistan, which dated back to the era between 1000-1400 CE.

The two cities, Tugunbulak and Tashbulak, are located in the Malguzar mountain range, about 2,100 meters (7,500 feet) above sea level. Urban centers are rarely located over 2,000m above sea level, with only 3% of the planet's population living at or above that altitude.

The smaller city, Tashbulak, which covered about 12 hectares, is located five kilometers (3.1 miles) away from the larger city of Tugunbulak, which covered 120 hectares. The authors say Tugunbulak was one of the largest cities in central Asia during the early-medieval period.

LiDAR maps created highly accurate maps of Tugunbulak and TashbulakImage: SAIElab, J. Berner, M. Frachetti

"These would have been important urban hubs in central Asia, especially as you moved out of lowland oases and into more challenging high-altitude settings," said Michael Frachetti, an archeologist at Washington University in St. Louis, US, who led the research. 

The two cities were likely important trading centers and fortresses protecting merchants traveling along the Silk Road, the authors say.

"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," Frachetti said in a press statement.

LiDAR allowed creation of archeological maps

This was the first-ever use of cutting-edge drone-based LiDAR in Central Asia. LiDAR is a detection method that uses light pulses to measure distances to the earth, in this case from a drone. 

The pulses generate 3D maps of the landscape beneath, including buildings and evidence of settlement, with very high accuracy at the centimeter-level scale.

"These are some of the highest resolution LiDAR images of archeological sites ever published," Frachetti said.

The scans created detailed views of plazas, fortifications, roads and houses that shaped the lives and economies of highland communities, traders and travelers.

The maps have been cross analyzed with archeological findings from the two cities, providing clues about their importance as industrial and economic hubs in central Asia. 

Preliminary digging at one of the fortified structures at Tugunbulak suggests that the fortress might have been a factory where local metalsmiths turned rich deposits of iron ore into steel.

The researchers also suggest the city's proximity to large forests indicates it could have been an important center for trading fuel.

Frachetti hopes to use the same combination of on-the-ground detective work and drone-based LiDAR to gather evidence of other high-altitude settlements along the Silk Road and beyond.

"We could really change the map of urban development in medieval Asia," he said.

Archeological digs at Tugunbalak and Tashbulak have revealed vibrant, industrial urban centers high up in the mountains.Image: M. Frachetti

What are the Silk Roads?

The cities were thought to have been constructed around 1000 CE during the time of the Qarakhanid Empire. The cities went into decline and disappeared sometime before Genghis Khan's Mongol forces conquered the region around 1220 CE.

"Major political forces were at play in Central Asia. The complex heart of the network was also a driver of innovation," Frachetti said.

Tashbulak and Tugunbulak were up in the mountains, away from the main overland routes of the Silk Roads, which passed by the lowlands near Samarkand. But the researchers argue the highland cities were not remote backwaters, but important trading centers in their own right.

The Silk Road is credited with bringing advanced technologies like gunpowder, paper, and silk from China to the Middle East and Europe. The trade routes also acted as conduits for religions like Islam, Christianity and Buddhism, as well as for artistic influences in sculpture, handicrafts and painting.

But some scholars say the impact of overland Silk Road routes has been overestimated — in part because ships along maritime routes from India could carry more goods than Silk Road carts and could also travel faster.

In his new book The Golden Road, historian William Dalrymple argues that ancient India has been overlooked as a center of ideas and technologies that transformed cultures around the world.

Dalrymple credits ancient India with spreading the first universities, the mathematical sign for zero and the other numbers generally called 'Arabic numerals', as well as games like chess and ideas of theoretical science. 

Edited by: Derrick Williams

Primary Source:

Frachetti, M. D., et al., (2024). Large-scale medieval urbanism traced by UAV–lidar in highland Central Asia. Nature. https://doi.org/10.1038/s41586-024-08086-5