The Walls and Moat
Top of the wall at the southwestern corner tower
The role of the Palace City was to provide an abode for the emperor and his family as well as to serve as the official place for receiving foreign dignitaries and conducting state affairs.
Even the Palace City was equipped with a surrounding wall, which separated the emperor from his supporting government officials and people at large. The walls stood almost eight meters tall, and were readied for a defensive battle despite already being heavily protected by all the walls of the Imperial City and of the Inner City.
Guard troops could patrol on top of the perimeter wall to catch intruders and guarantee the safety of the emperor and his family. Horse ramps were available at the northern gate (Shenwumen) and the southern gate (Wumen) so that horseback patrols had easy access to the top of the wall and increase the efficiency of the patrols.
The 52m wide and frozen moat at the NE corner
bathed in the early morning winter sun
To further boost defense the Palace city was encircled by an impressive 52 meter wide moat, which would have to be crossed undetected to even get near to the perimeter walls.
The corner towers were more decorative in nature than defensive structures.
Access was therefore in reality limited to the only four gates in the entire perimeter wall, which augmented the importance of controlling who could pass through the doors. These four entryways were heavily guarded day and night. Specially selected troops had the responsibility for the safety of the emperor and his family and, as was the case in other countries, it was considered an honor to serve as personal guard of the regent.
Red Truncheons
Two guards equipped with red truncheons were seated outside each of the four gates around the clock. They would only rise when a member of the imperial family would pass by.
If a person without proper authorization attempted to trespass the gate the guards would beat him severely with their red truncheons
Access Passes
Access to the Palace City was a serious and quite restricted matter, particularly in the Ming dynasty (1368-1644).
Access was somewhat loosened up in the Qing dynasty (1644-1912), but entry was only possible at the correct gate and doorway.
Even ministers with access rights had to present a certificate evidencing their name and rank.
All who passed through a gate, from the most senior Eunuch to the lowest laborer, had to wear a wooden identification tag hanging visibly from their waist and issued by the Imperial Household department.