I recommend the German-Russian Museum in Berlin-Karlshorst. The May 9, 1945 surrender that included the Soviets who were represented by Zhukov took place here. The surrender table, flags, etc are all preserved and displayed here. There is also a war museum with artifacts from the Soviet-Nazi war. Many tanks are displayed outside. It is on a former Soviet Air base and the building was once the Officer's Club. It was once a Soviet era museum and is reminiscent of those found in the former Soviet Union.
The Stasi Museum is also very good. It is in the former Stasi HQ and the archives are next door.
A drink or even dinner at the top of the tall tower at Alexanderplatz is a good way to end the evening.
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