Guoqing YangYang Guoqing is deputy research director at the Center for the Protection of the City Wall of Nanjing. For 15 years he has been engaged in the research of the city wall, and has visited more than 200 city walls at home and abroad. The research result by Guoqing have been published in the form of articles, essays and monographs. In 2011, at the invitation of the Institute for the History of Science of the Max Planck Institute, he conducted a comparative study in Germany on the history and current situation of the city walls in China and Germany. Read More Read Less