The Xi'an City Wall is the most complete city wall that has survived in China, as well being one of the largest ancient military defensive systems in the world. When Zhu Yuanzhang, the first Emperor of the Ming Dynasty (1368-1644), captured Huizhou, a hermit named Zhu Sheng admonished him that he should 'built high walls, store abundant food supplies and take time to be an Emperor,' so that he could fortify the city and unify the other states. After the establishment of the Ming dynasty, Zhu Yuanzhang followed his advice and began to enlarge the wall built initially during the old Tang dynasty (618 -907), creating the modern Xian City Wall. Initially, the wall was built with layers of dirt, with the base layer including also lime and glutinous rice extract. Throughout the time Xian City Wall has been restored three times. In 1568, Zhang Zhi (the government officer of that period) was in charge to rebuild the wall with bricks. In 1781, another officer, Bi Yuan, refitted the city wall and the gate towers. More recently (since 1983) the Shaanxi Provincial Government restored the city wall again. A circular park has been built along the high wall and the deep moat. The thriving trees and flowers decorate the classical Chinese architecture of the wall, adding additional beauty to the city of Xian. A nice suggestion for tourists: Try biking on the City Wall, you will have an enjoyable and interesting experience.