Very different – like those in Cracow and those in Gdansk? (5,5)
I believe the answer is:
poles apart
'very different' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for poles apart that I've seen before include "having nothing in common" , "some Europeans?" , "with widely differing views" , "Differing greatly" , "Incompatible" .)