Mutianyu is located in Beijing's Huairou County northeast, because location is very important, Mutianyu protect Beijing's military since ancient times is the hub of this paragraph west Beijing Great Wall Juyongguan Changping County, east of Beijing Miyun County gubeikou for the construction of the Ming Dynasty, is the capital of the eastern section of the north gate Huanghua Town, known since ancient times surround the capital, the imperial tombs of the northern barrier, one of the important juncture. Is known as the "crises Ridge Xiongguan." This has happened many times in the war, most notably the Ming Dynasty several wars. Ming Yongle (1404), where the set is off, the Great Wall is built in the mountains above. Because in the valley looked up, as if on the day can be accessed, named Sky Valley (Valley) Off, Ferris and Mu Tian nearly as sound, and the valley and valley are homophones, later called Mutianyu (Valley) closed. Great Wall north of the village, built in the Northern Qi, Sui-generation has been repaired many times. Ming Yongle built the Mutianyu off, once in Jiajing demolition, and left "Mutianyu," the plaque. Wall rock hill with flowers, lime stone and other masonry materials. Sided forts, fortresses intensive artillery on the city of the Ming Dynasty, were built in double battlements battlements mouth perforation below the top of the arc was a square hole, both for the fight against the enemy, and easy to protect yourself. An old castle in the village, long width one hundred meters, is the only city-based.