Zhenbeitai. Zhenbeitai is the loftiest city platform of the Great Wall. It is 5 kilometers to the north of Yulin, shǎnxi Province. It was a most important pass in Yulin Town of the Ming Great Wall, clutching the gorge of the passage from south to north. It was built under the guidance of Governor Xu Zongjun of Yulin Town in 1607. The northeastern part of Zhenbeitai is connected with a castle. The castle is contemporary with Zhenbeitai. It was a Kuangongcheng (fund-tribute city), also called ‘the Hongshan Horse Market’. Kuangongcheng was the place where Mongolian leaders made negotiations with Ming officials. At the same time, it was also a place for official and folk trade of horses.
Zhenbeitai stands tall on the south side of the Maowusu Desert. It was a watch sentry protecting the trade of the Hongshan horse market. It has 4 floors and is like a pagoda in shape, decreasing from bottom to top. The full height is 28.5 meters. The side lengths of the foundation are 82, 76, 64 and 64 on the north, south, east and west sides. The perimeter is 320 meters, and the depth is 12 meters. The whole city platform was laid with grey bricks outside. On each floor there are battlements. On the second floor there is an arched door facing the south that leads to the top. Each ceiling was built several meters upward and narrower for the next floor’s base. The four floors are different in height. From bottom to top they are 10.74, 11.35, 4.15 and 4.4 meters respectively.