This undated photo shows a hidden door of the Huangyaguan section of the Great Wall in north China's Tianjin. Ruins of over 130 hidden doors on the Great Wall, one of the world's great wonders, have been recently unveiled through close to centimeter-resolution continuous shooting, said a research team on the Great Wall's defense system on Wednesday. (Tianjin University/Handout via Xinhua)
Go to Forum >>0 Comment(s)