What is a proper noun of the common city?

You're asking for a proper noun that represents a common city. Here's how to understand that and some examples:

* Common Noun: A general name for a person, place, or thing (e.g., city, river, mountain).

* Proper Noun: A specific name for a person, place, or thing, always capitalized (e.g., London, Mississippi River, Mount Everest).

So, you're looking for a specific city name. Some examples could be:

* London (a common city name is "capital")

* Paris (a common city name is "city of lights")

* Tokyo (a common city name is "megacity")

Let me know if you have a specific common city name in mind, and I can give you the proper noun!