Address: Sihai Town, Yanqing District, Beijing

Located on the main peak of the Flaming Mountain in Sihai Town, Jiuyanlou Watchtower, 1141 meters above sea level, is the largest hollow watchtower of Great Wall. It is the ancient military strategic fortress. Jiuyanlou Watchtower was the junction of the Great Wall of Ji Town, Chang Town and Xuan Town, and the intersection of the inner and outer Great Wall in the Ming Dynasty. It can be referred as the "Beijing Knot".

There was a record about the Jiuyanlou Watchtower dated back to the second year of Emperor Chenghua's reign in the Ming Dynasty (A.D.1466), with a long history of more than 500 years. The existing Jiuyanlou Watchtower has only one story, with height of 7.8 meters and 13 meters each side. The lookout hole is 1.65 meters high and 0.5 meters wide, and there is a circular path with the width of 1.2 meters. With its nine archery windows, Jiuyanlou Watchtower is a natural viewfinder frame. On sunny days, you can even overlook the city of Beijing, so it is also called "Wangjing Tower". Climbing the Great Wall and looking far away, you can have panoramic view of Mutianyu section and Jiankou section surrounded by hills and valleys. Whether it is sunny or rainy, visitors will be able to admire different wonderful natural landscapes.