Yeah, I'd happily go back for a third time. The first trip I did I ventured out to place called
Nowa Huta on the tram. A Joseph Stalin commissioned 'New Town' meant to essentially be a bit of a propaganda piece to be a showpiece of the communist ideal of a Town built by workers for workers. Huge defunct steelworks there. The town is fascinating, well preserved Soviet era architecture and nothing like the main city.
I'd like to go to Warsaw, Wroclow and Gdansk as well, I've been told all are great.