Hanguguan military pass relics of Eastern Han Dynasty (AD 25-220), Luoyang, Henan province. Photo provided to China Daily

6. Hanguguan military pass relics of the Eastern Han Dynasty (AD 25-220), Luoyang, Henan province

This military pass leading to the Silk Road had important strategic significance, and has been repeatedly documented in historical files. The excavation found 17 sections of walls built by rammed earth and two ancient roads and a large number of other construction components. The eastern wall is 22 meters thick. One road was rammed as many as 12 times, and was 2.3 meters thick. Clear evidence of former residents' activities was also detected.

"Studies on ancient military passes are severely lacking in China," says Yan Hui from the Luoyang Municipal Institute of Archaeology. "This discovery provides an important reference to further relevant academic research and relic protection, and will probably help the ancient Silk Road bid for UNESCO World Heritage."