It means that most people don't appreciate how good the city really is.

But underatted means like good but a lot of people don’t notice how good it is For example this game is underatted Meaning it’s good but people don’t notice it’s value of how good it is If someone says overatted it’s the complete opposite

It’s American slang(slang being words only used in certain areas of America which “underatted being that word) use urban dictionary for slang words like that

It means people do not recognize how good or important the city really is.