During my trip to Berlin I also visited Sanssouci Park in the nearby city Potsdam with its numerous castles of Prussian kings. If you are interested in European history I strongly recommend to visit the “Friederisiko” exhibition in the Neues Palais (where I spent four hours, unfortunately no cameras wehere allowed inside the exhibition but it is well worth a visit – feels like a time travel!).
You are good !!!!!!!!!!!!!