Mysterious Section of the Great Wall of China Isn't What We Thought, Study Reveals

A mysterious section of the Great Wall of China has unveiled some of its secrets thanks to a years-long intensive survey. As it turns out, the new research raises more questions than it answers.

A team of archaeologists at the Hebrew University of Jerusalem in Israel and the National University of Mongolia have studied a 405-kilometer long wall in Eastern Mongolia called the Mongolian Arc—a portion of the Great Wall with a history and purpose that, until now, were largely unknown.

Previous research, based on ancient texts, suggested that the wall may have been defensive but new evidence uncovered through this study suggests it wasn’t—although its exact function is still enigmatic. 

This latest study, published in December 2023 in the Journal of Field Archaeology, is part of a wider project looking to understand why and how ancient empires built these mammoth structures, and what impact that had on the social, political and economic environment of the time.

Part of the study involved mapping the arc using satellite images from Google, Bing, geographic information systems (GIS), and declassified US spy images from the 1960s; as well as Chinese atlases and Soviet maps. This was a crucial first step because, as the authors wrote in their study, “if mentioned at all, this wall section and its associated structures are either unrecognized or incompletely and inaccurately documented in existing literature.”

Combined with extensive and detailed surveys done on the ground and by drone, researchers described the wall as up to 1.5 meters tall, although usually much more worn-down and barely visible, 2.5 meters wide at the top and flaring out to just shy of 14 meters at its base. A trench runs along the northern side and 34 structures dot its length. Around a quarter of the wall’s 405 kilometer length is made up of gaps.

Compared to its southern neighbor, the Mongolian Arc is seemingly unimpressive. “These walls are not as impressive as the popular imagery of the Great Wall of China may have us assume,” the authors wrote, describing it less as a wall and more of a “pile of earth”.

Yet its modest construction reveals a fascinating past. For example, most of the structures don’t have a line of sight with other outposts and are in low-lying areas of the wall, suggesting they weren’t used for combat or defense but maybe rather for moving animals or people along streams. Potentially, the authors suggest, they could have been used for collecting taxes or keeping an eye on where civilians were migrating. 

And the majority of the gaps they identified aren’t from the wall fading away but rather were never built in the first place. The gaps are too wide for moving people or animals, so the authors still aren’t sure what their purpose was. 

It’s also still unclear when the wall was built. Historical texts from the Liao (Liaoshi 遼史) and Jin (Jinshi 金史) dynasties put construction somewhere between the 11th and 13th centuries, but there’s currently no archeological evidence to back this up. 

The researchers are now planning test excavations of the structures and the wall, to get a better idea of when it was constructed, how long and what it was used for. They’ll also employ even more sophisticated mapping technology, including photography that can capture many different wavelengths of light, to figure out more about the mysterious gaps.