collinsdictionary.com:
(1) I'll look you up when I'm in town.
As I understand, "town" is the definite town which is known to both the speaker and the listener.
So "town" must have "the".
Why does it not have "the"?
my variant:
(2) I'll look you up when I'm in the town.
What is the difference between (1) and (2)?