The Songliao border Guangu tunnel was previously the underground passage for military defense during the Song and Liao periods. The tunnel goes from southwest to northeast across Xiongxian, Bazhou, Wen'an and other counties. It is grand in scale, multi-type, complicated in structure and complete in warfare. It is especially worth mentioning that the water tank in the tunnel, in addition to its daily use, has a more important use in wartime - monitoring the enemy. The cylinder is covered, and the soldiers put their ears next to the bottom of the tank, and they can hear the sound of distant horses.