Zoo Berlin
They don't have a panda any more, but still a great zoo.
Mr. Gorbachev, tear down this wall.
https://m.youtube.com/watch?v=LA0X4SliFJI
If you like aviation, a visit to this military museum wouldn't be bad. Mainly focus on the history of Luftwaffe and Bundeswehr.
Plenty of airplanes from WW1 biplanes to WW2 BF-109 fighters. Also some post-war jets.