Braving subzero temperatures, 46-year-old Zhao Yong and his dog Heilang ("black wolf"), patrol the Dalt ancient city ruins in Qagansum village in Northwest China's Xinjiang Uygur autonomous region.

Situated in the suburbs of the city of Bole, Dalt ancient city spans 200 mu (around 13.33 hectares) and was once a vital hub along the ancient Silk Road.

Archaeological research suggests that this ancient city dates back to between the 10th and the 14th centuries. It was designated a national key cultural heritage protection site in 2013.

The ruins include inner and outer walls. The inner walls are reasonably intact, and include rammed earthen buildings, and brick structures that resemble bathing places.

Efforts to protect this historical treasure began decades ago, spearheaded by Zhao Yong's father, Zhao Yuecai.