Me and my siblings total of 3 ( all are adults) will be travelling in september to germany, will be our second time, last visited bavaria area. We will have 3 weeks time in total. mostly focus in the north part and black forest esp heidelberg , berlin, potsdam ,schwerin , bremen.
wk 1: arrived in berlin, may stay for 1 day , then to Cologne--stay 1 week and will do outskirts trip : to bonn, muster, gotttingen.
wk2. back to berlin on 6th day , then one of siblings will join us, stay in berlin for 5-6 days , explore potsdam, berlin, hopefully to schwerin for castle and bremen, bremenhaven.
wk 3: heidelberg, triberg and gengenback , on 6th day, back to berlin and fly home.
All of us are interested in medival old towns, Cathedrals, Dom, reigsdat and senic train ride along rhine river ( hopefully from frankfurt to heidelberg).
WE are not quite into parks or zoo or shopping.
any suggestions to tune up this trip? we will get the german rail pass for 3 days major for berlin to heidleberg and cologne to berlin. Thanks in advance