Interior view of ancient underground military tunnel in Bozhou, Anhui

Photo shows an interior view of the ancient underground military tunnel in Bozhou, east China's Anhui Province, Aug. 4, 2021. The underground military tunnel built in the late Eastern Han Dynasty (25-220) by Cao Cao, a famed warlord, is located underground in the old city of Bozhou, and extends out of the city in a cross shape. The tunnel is one of the oldest and most well-preserved underground military facility in China, listed as a major historical and cultural site protected at the national level. (Xinhua/Huang Bohan)