First built in the Northern Song Dynasty, the walls of Zhaoqing City, Guangdong Province, have stood for nearly 1,000 years, witnessing the ebb and flow of the fortunes of Zhaoqing and the development of Lingnan culture. It was once the seat of the governor-general's office of Guangdong and Guangxi during the Ming and Qing dynasties. The walls stretch for 2.8 kilometers. After several major rounds of renovation and expansion work over the centuries, the current walls are primarily brick, with other structures and buildings made of clay, stone or wood. The highest point of the walls is the Piyun Tower ("wearing the cloud" in Chinese), where visitors gather to take photos as the glow of sunrise and sunset paints its roof gold.