Archeologists brought to light some 500 cannons and grenades in a Great Wall barracks at its Jiuyanlou section in Yanqing County, Beijing, when a Great Wall survey team reached a most important location here. The on-going survey is considered as the most comprehensive and accurate one in history. 　　
　　
　　The barracks covers an area of 2,500 square meters and so far, archeologists have discovered 12 rooms there. Stone tablet remains here show that the camp was built during the reigning years of the Wanli emperor in the Ming Dynasty. Archeologists found some 500 things made in the Ming Dynasty, including architectural remains, daily-use articles, cannons, shells, grenades, etc. Experts say that ancient soldier quarters were usually located in the inner part of the Great Wall, and this is the first time for them to discover soldier quarters built on the wall body. 　　
　　
　　The Jiuyanlou Great Wall section was built in 1543, or the 22th reigning year of the Jiajing emperor in the Ming Dynasty. Located on a hill in Fendie Valley, southeast of the Sihai town in Yanqing County, it has the largest watch tower and greatest number of crenels ever found. On the Great Wall remains uncovered here include rubbles, bricks, and table ware. According to on-site measurement, the tower measures 7.8 meters high and 13 meters wide. There are nine crenels on each side of the tower, thus local people call it Jiuyanlou, or the "nine holes tower". 　　
　　
　　With simple measuring tools, a team of experts carried out a survey of the Great Wall in 1984, which showed that the Great Wall was 629 kilometers long in the Beijing section. On March 17, 2006, experts started to conduct another survey. Since the survey was more comprehensive and detailed this time, experts predict that many more important relics and sites might be uncovered.