trg

1. square; plaza
   Nađimo se kod konja na Trgu republike. — Let's meet by the horse on Republic Square.
   Na glavnom trgu je bio koncert. — There was a concert on the main square.
2. dated marketplace
   Seljaci su nosili robu na trg. — The peasants took their goods to the marketplace.

The usual phrase is "na trgu", "on/in the square".