You’re Kraków, so it might not make much sense suggesting Mazury (this would be more for the Mazowsze and Pomorze people). If it will be hot, i’d recommend heading up the A1 and check out Brodnica and its surroundings (it’s Kujawsko-Pomorskie, but has all the atmosphere of Mazury proper, with a hint of ziemie lubawskie). If not to hot, i’d be touring Lubelsczyzna 😉