principalCityOf

Given a predicate that represents a relationship or action between entities, generate a one-sentence description explaining its meaning.  
# Instructions
Focus on describing the relationship, not the entities themselves. 
# Response Format
Begin the description with \' Indicates...\'

Predicate: principalCityOf

Indicates that a city serves as the main or most important city (often administrative, economic, or cultural center) of a specified region or area.