Aerial photo taken on July 20, 2018 shows a watchtower on the city wall in Pingyao, north China's Shanxi Province. Pingyao is a tourist attraction located about 600 kilometers southwest of Beijing, capital of China, with a history dating back some 2,700 years. Its old town is famous for its well-preserved city walls and was added to the UNESCO World Heritage Site List in 1997. (Xinhua/Tao Ming)