Qianmen (前门), or the Front Gate, consists of a pair of gate-like towers, the northernmost being the 40m-high Zhengyang Gate, which was also the largest of the nine gates of the Inner City Wall and the only gate proper that still stands, and the Zhengyang Gate Arrow Tower, just south of here. The gate can be climbed for fine views of the square and houses a museum charting the history and demise of Beijing's city fortifications.
With the disappearance of the city walls, today the gate sits out of context. Fortifications would have been joined it to the Zhengyang Gate Arrow Tower in front, and the Inner City Walls would have stretched away east and west, separating the inner, or Tartar (Manchu), city from the outer, or Chinese, city. Partially destroyed in the Boxer Rebellion in 1900, the gate was once flanked by two temples that have also since vanished.
On the second of its three exhibition floors is a fascinating timeline, including historical photographs showing the area as it was at the beginning of the last century. Explanatory captions are in English as well as Chinese.