Been to London? or Been in London?

(a) Have you ever been to London?
(b) Have you ever been in London?
A friend asked me the difference between the two. Initially I thought (a) was the correct way of saying it, but sometimes I have heard people say it as in (b)
Why is it okay to say:
Have you ever been to Harrods in London?
Or whilst speaking on the phone to someone, "are you still in London?"
Why is it okay to use "...in London" in this context and not as in (b) above?
This has perplexed me greatly, can anyone help?
Thanks in advance

to London- movement, travelling
in London- location

This is my guess:

Have you ever been to London?
Have you travelled (or visitied) London. It could be a short trip.

Have you ever been in London?
Means, have you lived in London. It could be for a longer period of time.

Is this correct?

Quote:

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Originally Posted by karthikesh

This is my guess:

Have you ever been to London?
Have you travelled (or visitied) London. It could be a short trip.

Have you ever been in London?
Means, have you lived in London. It could be for a longer period of time.

Is this correct?

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The first part is correct, but the second has nothing to do with living there. One could use "in London" to clarify that someone was not in the general vicinity of London.

A: Have you ever been to Chicago?
B: Yes, I was at O'hare airport.
A: That's in the suburbs. Have you ever been in Chicago?
B: No, not the city proper.

to london -- may be because of sentence indicates travelling
in london -- indicates living in london

It makes sense. Hopefully, I'll remember and apply properly in the future. Thank you.