Student or Learner
Imagine that you are visiting a new city for the first time as a tourist, whether it be Paris, London, Sydney, Rome, or New York City.
I don't understand the whole sentence too well, however, I can imagine what they are talking about. Anyway, I don't understand why "be" was used there, at all! I'd say "it is" instead?
Why was "be" used there?
Because we are imagining various possibilities, the subjunctive be is used. Whether to use "be" or "is" may simply be a matter of style.
I'm not trying to make a big deal out of this but in English we can imagine in many ways without using the subjunctive.
If you are visiting; Say you're/were visiting; Imagine you are/were visting' Pretend you're visiting, ...
There is nothing magical about the subjunctive. There are a few remaining forms left over from older forms of English. For each subjunctive form that still exists, English has at least one other way of describing the same situation.
The subjunctive is not always needed, nor is it always desireable and it certainly isn't always the "correct" form.
I've never seen such a pattern (which doesn't mean it's wrong of course), I mean whether it be. Sure it's the Subjunctive, only if I were asked to correct it, I'd write
... as a tourist, be it Paris...