Complex sentence: The player starts with one city, but with a higher position in the game, they can build'sub-cities' on flat ground, the max amount of sub-cities you can have is two, regardless of how high your position is.
Split into simpler sentences: The player starts with one city, but with a higher position in the game, they can build'sub-cities' on flat ground. The maximum amount of sub-cities a player can have is two, regardless of how high their position is.