I ran my code on 28 May 2021. There were 345553 users in rating list. 87427 of them set field City in their profiles. There are 4009 unique values. Certainly some profiles might have fake values but anyway it is interesting to look at all these points on the map. Cities are marked by circle if there is at least one Codeforces user profile with this city name.
.
But what's about active users? There were 44188 of them, 13108 set City in their profiles. There are 1607 unique values.
It is rather impressive to compare active users map with actual global conflict map. The screenshot below is from Global Conflict Tracker site. Codeforces users keep participating in contests even upon the very bad circumstances.
C137 has been living in Syria. He is my guest for next interview.
now i'm interested what is the biggest city in Russia/India/Europe without a registered user
I'm surprised to even see that there exist some cities in India where nobody uses codeforces!
Obviously, India is a large country, so there will be SOME places with unregistered users. The size of the Indian mainland is vastly underestimated.