This section focuses on the Mongolian Arc, a 405 km-long segment of a broader frontier system spanning over 1,500 km across present-day Mongolia and northern China. Located in Dornod and Sukhbaatar provinces, the Arc was surveyed in 2022 following satellite imagery analysis and remote sensing. During the survey, 34 rectangular enclosures were identified along the wall line—most of them directly associated with the fortification.

Excavations were carried out in 2023 at two sites, MA03 and MA20. Radiocarbon dating from MA03 indicates that the Mongolian Arc dates to the early Jin dynasty (1115–1234). The enclosure walls and internal structures were built using pounded earth and stone, while the wall itself, at least in the excavated area, appears as a shallow trench rather than a formal rampart. These findings offer valuable insights into the construction, function, and historical context of the Mongolian Arc.

Below, an interactive map presents the survey data along the Arc. Further down the page, an additional interactive map and excavation data are provided for the two investigated sites, MA03 and MA21.