What are the 4 concentric rings that surround the Forbidden City?

The four concentric rings surrounding the Forbidden City are the Imperial City, the Inner City, the Outer City, and the moat. The Imperial City houses the Forbidden City itself, which was the emperor's residence. The Inner City includes the living quarters of the imperial family and important governmental structures. The Outer City served as a residential area for common citizens and merchants, while the moat provided additional defense and separation from the surrounding areas.