Learn Croatian: Kuda idemo u centar? - Which way are we going to the center?

Kamo asks for the final destination (where to), while kuda asks for the route or direction (which way). Because the destination is already stated in the sentence (u centar), the speaker is asking about the specific path or route they will take to get there.

The translation says 'to the center', so why does the Croatian use the preposition u (in) instead of do (to/until)?

In Croatian, you typically use u (into) or na (onto) with the accusative case to express going to a destination. Do usually implies going up to the edge of something or as far as a certain point, whereas u centar implies entering the center itself.

Why is it u centar and not u centru?

Because the verb idemo (we are going) shows motion toward a destination, the preposition u must be followed by the accusative case. For masculine inanimate nouns like centar, the accusative looks exactly like the dictionary form. If you were already hanging out in the center (location without motion), you would use the locative case: u centru.

I often hear native speakers say Kuda ideš? to mean 'Where are you going?'. Is that correct?