Final answer:
In the game Rise of Kingdoms, the City Hall can be upgraded to a maximum level of 25, which unlocks various features and improvements for the player's city.
Step-by-step explanation:
The highest level a City Hall can reach in Rise of Kingdoms is level 25. To grow the city and unlock new features, players must incrementally upgrade their City Hall, which is a core building in their city. Upgrading the City Hall allows access to new buildings, higher levels for existing structures, and additional march queues, among other benefits.