>>You didn't say "a historic city" but "the historic city"... i.e. the one.
If I say "the People's Republic of China," that doesn't mean that China is the only People's Republic. "The" refers to the whole element, not just the first part. IOW "the (historic city of Basel)" not "(the historic city) of Basel."
>>By the way, does Basel have anything else but its city? How is the rest called if there's the city of it?
Technically the agglomeration of Basel extends into France and Germany so yes, it does have more than just the Swiss city. But I get your point: yes, more English language quaintness. ;-)
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
