Whenever the city layout of Beijing is mentioned, its iconic central axis will immediately come to mind. This imaginary central axis, with a length of 7.8 kilometers, is the longest and best-preserved central axis in the world.
From the south at Yongdingmen Gate to the north at the Drum Towers, almost all of those important sites are strung by the central axis of Beijing. It passes through Zhengyangmen Gate (popularly known as Qianmen), Tian'anmen Gate, Duanmen Gate, Wumen Gate (the southernmost entrance to the Forbidden City). From Wumen Gate, it continues north through the Forbidden City until reaches north gate, Shenwumen Gate. It then passes through Longevity Pavilion atop Prospect Hill (Jingshan) and ends at the Drum and Bell Towers.
In ancient times, the central axis, which was popularly known as the "dragon vein," was seen as a royal line. According to Chinese tradition, the central axis is a fixed line. Traditional thinking holds that the north-south axis coincides with the Earth's meridian. A number of grand royal buildings were built along the axis with the Forbidden City at the center. Emperors in ancient China believed they were the center of the world, so all their palaces should be built there.
This central axis splits the city into approximate halves, each of which was built in Ming times with symmetrically arranged pairs of gates. Although the gates have been torn down to make way for modern roadways, their names are still used to designate city districts: for example, Dongzhimen and Xizhimen, Fuchengmen and Chaoyangmen, and Xuanwumen and Chongwenmen. It is curious to note that the central axis passing through Tian'anmen lies approximately 200 meters east of the true axis of symmetry as calculated from the distance between the city walls.
Most of the gates along the central axis are well preserved, except for Di'anmen Gate and Yongdingmen Gate which were torn down to make way for road projects in the mid-1950s. However, Yongdingmen Gate regained its former grandeur after it was rebuilt in 2004. Now, Di'anmen Gate is the only part of the backbone that still needs to be restored.
Di'anmen gate was first built in 1420. It is the north gate of the imperial city (a special zone surrounding the Forbidden City where ordinary people were not allowed to enter) of old Beijing while Tian’anmen is the south gate. The names of these two gates in Chinese symbolize the peace of heaven and earth. The Beijing Government is preparing to apply for World Cultural Heritage status for Beijing's central axis. As part of this effort, Di'anmen Gate will be restored.