The Great Wall

The Great Wall is the world's largest man-made structure and one of the most visited places in China

Badaling section of the Great Wall

The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe. Several walls were being built as early as the 7th century BCE; these, later joined together and made bigger and stronger, are now collectively referred to as the Great Wall. Especially famous is the wall built 220–206 BCE by Qin Shi Huang, the first Emperor of China. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained, and enhanced; the majority of the existing wall is from the Ming Dynasty(1368–1644). - in: wikipedia

Wangjinglou section of the Great Wall

 Watching Beijing Tower (Wang Jing Lou): At an elevation of 986 meters, it is regarded as the summit of the Simatai Great Wall as well as the highest cultural relic in Beijing. Its name comes from the fact that at night (with good visibility), one can see the lights of Beijing shimmering in the distance 120 km away. The bricks used to build the walls here even stamped with the date on which they were made and the code numbers of the armies that made them.

Simatai, a section of the Great Wall of China located in the north of Miyun County, 120 km northeast of Beijing, holds the access to Gubeikou, a strategic pass in the eastern part of the Great Wall.

Originally built during the Northern Qi dynasty (550–577) and rebuilt in the Hongwu years of the Ming dynasty. - in: wikipedia

Badaling section of the Great Wall

 Badaling is the site of the most visited section of the Great Wall of China, approximately 80 kilometres (50 mi) northwest of urban Beijing city in Yanqing County, which is within the Beijing municipality. The portion of the wall running through the site was built in 1504 during the Ming Dynasty, along with a military outpost reflecting the location's strategic importance. The highest point of Badaling is Beibalou, approximately 1,015 metres (3,330 ft) above sea level. - in: wikipedia

Watchtower at the Jiayu Pass

Jiayu Pass is the first pass at the west end of the Great Wall of China, near the city of Jiayuguan in Gansu province. Along with Juyong Pass and Shanhai Pass, it is one of the main passes of the Great Wall.

A fabulous legend recounts the meticulous planning involved in the construction of the pass. According to legend, when Jiayuguan was being planned, the official in charge asked the designer to estimate the exact number of bricks required and the designer gave him a number (99,999). The official questioned his judgment, asking him if that would be enough, so the designer added one brick. When Jiayuguan was finished, there was one brick left over, which was placed loose on one of the gates where it remains today.

The structure was built during the early Ming dynasty, sometime around the year 1372. The fortress there was greatly strengthened due to fear of an invasion by Timur, but Timur died of old age while leading an army toward China. - in: wikipedia