Potsdam with its spectacular royal palaces and parks, the Dutch Quarter is a lovely city and a UNESCO World Heritage Site.
The Spreewald, a unique landscape with hundreds of small irrigation canals, a UNESCO biosphere reserve.
Castles and Palaces: There are many smaller and larger rural palaces and castles, some of them are hotels, others museums or private homes; in the Fläming region, there are four medieval castles.
Historic city centers: many towns in Brandenburg have pretty well kept historic city centers.