Berlin - must see or dos

[Cottoneyed12]

We go to Berlin in the morning for two nights. Any recommendations of must dos

The Olympic stadium was my favourite thing. Great from a historical perspective (built by the nazis for the 1936 olympics in 9 months flat). Also great for footy mad boys as is a working football stadium (home to hertha Berlin).

Also second the Berlin card and the reichstag (book in advance).