I'm not saying that 'this' doesn't resolve to anything.

Of course it does. It's like pointing to something and asking 'what's this?'. Of course the act of pointing, or the act of standing in a city resolves 'this' to something else.

But the point is where 'this' resolves to something which has meaning.

A question makes sense, if it is understandable and answerable.

Q1: //TODO

Q2: what's the population of this city ?

Q3: what's the location of this city ?

...

Q22: what's the altitude of this city?

Q23: what's the weather in this city ?

Suppose I ask you "What is the answer to Question 23?".

You'll respond "what is Question 23?" (trying to resolve/concrete 'Q 23').

I'll reply "Question 23 is - 'What's the weather in this city?' ".

You'll respond "well, what does 'this' refer to in Question 23?" (trying to resolve/concrete pronoun 'this')

I'll reply "this refers to the city in Question 22"

You'll respond "well, what is Question 22?' (again trying to resolve/concrete 'Q 23')

I'll reply "Question 22 is - 'What's the weather in this city?' "

You'll respond "well, what does 'this' refer to in Question 22?" (again trying to resolve/concrete pronoun 'this')

So-on, so-forth.. until we reach Question 2, referring to Question 1.

Now, If I define question 1 to be - 'What is the capital of USA?'. Then, by chaining, you can answer Question 23.

But if it do not define question 1, you can't answer Question 23, because I have not given you enough information to resolve pronoun 'this' in 'this city'.

That is the case with OP's question. In order to answer a question, the question must be answerable. In order for a question to be answerable, it must be understandable. In order for a question to be understandable, all pronouns in it must be resolvable to a valid question.

Do you agree that the question 'what is his height?' - is unanswerable IF the asker is not pointing to anyone, or there is no one else in the room, or there is no prior context - because the pronoun 'this' is unresolved ?