The Berlin Wall is mostly gone – but there are still a few sections left around the city. You can go and visit one right at the Nordbahnhof where there is also a small museum.
Close to the Brandenburger gate you will find a small Soviet war memorial from World War II. You can just walk five minutes down the street from the Brandenburger gate to get there.
Checkpoint Charlie was the most famous of the checkpoints between East and West Berlin during the cold war. It was here some of the most famous standoff between east and west took place.
At Nordbahnhof in Berlin you will find a small museum about how the subway system were run during the time of the Berlin Wall.
There are many castles around Potsdam. The most famous one is Freiderick the Great favorite castle – the Schloss Sanssouci.